Cricao de Sites - 650 Layouts Prontos/WebMasters.iso/Blogs/wordpress2.6.exe/wordpress2.6/wp-includes/post.php

PHP Script | 2008-08-13 | 95.6 KB | 3,446 lines

<?php
/**
 * Post functions and post utility function.
 *
 * Warning: The inline documentation for the functions contained
 * in this file might be inaccurate, so the documentation is not
 * authoritative at the moment.
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 */

/**
 * Retrieve attached file path based on attachment ID.
 *
 * You can optionally send it through the 'get_attached_file' filter, but by
 * default it will just return the file path unfiltered.
 *
 * The function works by getting the single post meta name, named
 * '_wp_attached_file' and returning it. This is a convenience function to
 * prevent looking up the meta name and provide a mechanism for sending the
 * attached filename through a filter.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.0
 * @uses apply_filters() Calls 'get_attached_file' on file path and attachment ID
 *
 * @param int $attachment_id Attachment ID
 * @param bool $unfiltered Whether to apply filters or not
 * @return string The file path to the attached file.
 */
function get_attached_file( $attachment_id, $unfiltered = false ) {
    $file = get_post_meta( $attachment_id, '_wp_attached_file', true );
    if ( $unfiltered )
        return $file;
    return apply_filters( 'get_attached_file', $file, $attachment_id );
}

/**
 * Update attachment file path based on attachment ID.
 *
 * Used to update the file path of the attachment, which uses post meta name
 * '_wp_attached_file' to store the path of the attachment.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 * @uses apply_filters() Calls 'update_attached_file' on file path and attachment ID
 *
 * @param int $attachment_id Attachment ID
 * @param string $file File path for the attachment
 * @return bool False on failure, true on success.
 */
function update_attached_file( $attachment_id, $file ) {
    if ( !get_post( $attachment_id ) )
        return false;

    $file = apply_filters( 'update_attached_file', $file, $attachment_id );

    return update_post_meta( $attachment_id, '_wp_attached_file', $file );
}

/**
 * Retrieve all children of the post parent ID.
 *
 * Normally, without any enhancements, the children would apply to pages. In the
 * context of the inner workings of WordPress, pages, posts, and attachments
 * share the same table, so therefore the functionality could apply to any one
 * of them. It is then noted that while this function does not work on posts, it
 * does not mean that it won't work on posts. It is recommended that you know
 * what context you wish to retrieve the children of.
 *
 * Attachments may also be made the child of a post, so if that is an accurate
 * statement (which needs to be verified), it would then be possible to get
 * all of the attachments for a post. Attachments have since changed since
 * version 2.5, so this is most likely unaccurate, but serves generally as an
 * example of what is possible.
 *
 * The arguments listed as defaults are for this function and also of the
 * get_posts() function. The arguments are combined with the get_children
 * defaults and are then passed to the get_posts() function, which accepts
 * additional arguments. You can replace the defaults in this function, listed
 * below and the additional arguments listed in the get_posts() function.
 *
 * The 'post_parent' is the most important argument and important attention
 * needs to be paid to the $args parameter. If you pass either an object or an
 * integer (number), then just the 'post_parent' is grabbed and everything else
 * is lost. If you don't specify any arguments, then it is assumed that you are
 * in The Loop and the post parent will be grabbed for from the current post.
 *
 * The 'post_parent' argument is the ID to get the children. The 'numberposts'
 * is the amount of posts to retrieve that has a default of '-1', which is
 * used to get all of the posts. Giving a number higher than 0 will only
 * retrieve that amount of posts.
 *
 * The 'post_type' and 'post_status' arguments can be used to choose what
 * criteria of posts to retrieve. The 'post_type' can be anything, but WordPress
 * post types are 'post', 'pages', and 'attachments'. The 'post_status'
 * argument will accept any post status within the write administration panels.
 *
 * @see get_posts() Has additional arguments that can be replaced.
 * @internal Claims made in the long description might be inaccurate.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.0
 *
 * @param mixed $args Optional. User defined arguments for replacing the defaults.
 * @param string $output Optional. Constant for return type, either OBJECT (default), ARRAY_A, ARRAY_N.
 * @return array|bool False on failure and the type will be determined by $output parameter.
 */
function &get_children($args = '', $output = OBJECT) {
    if ( empty( $args ) ) {
        if ( isset( $GLOBALS['post'] ) ) {
            $args = array('post_parent' => (int) $GLOBALS['post']->post_parent );
        } else {
            return false;
        }
    } elseif ( is_object( $args ) ) {
        $args = array('post_parent' => (int) $args->post_parent );
    } elseif ( is_numeric( $args ) ) {
        $args = array('post_parent' => (int) $args);
    }

    $defaults = array(
        'numberposts' => -1, 'post_type' => '',
        'post_status' => '', 'post_parent' => 0
    );

    $r = wp_parse_args( $args, $defaults );

    $children = get_posts( $r );
    if ( !$children )
        return false;

    update_post_cache($children);

    foreach ( $children as $key => $child )
        $kids[$child->ID] =& $children[$key];

    if ( $output == OBJECT ) {
        return $kids;
    } elseif ( $output == ARRAY_A ) {
        foreach ( $kids as $kid )
            $weeuns[$kid->ID] = get_object_vars($kids[$kid->ID]);
        return $weeuns;
    } elseif ( $output == ARRAY_N ) {
        foreach ( $kids as $kid )
            $babes[$kid->ID] = array_values(get_object_vars($kids[$kid->ID]));
        return $babes;
    } else {
        return $kids;
    }
}

/**
 * get_extended() - Get extended entry info (<!--more-->)
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.0.0
 *
 * @param string $post {@internal Missing Description}}
 * @return array {@internal Missing Description}}
 */
function get_extended($post) {
    //Match the new style more links
    if ( preg_match('/<!--more(.*?)?-->/', $post, $matches) ) {
        list($main, $extended) = explode($matches[0], $post, 2);
    } else {
        $main = $post;
        $extended = '';
    }

    // Strip leading and trailing whitespace
    $main = preg_replace('/^[\s]*(.*)[\s]*$/', '\\1', $main);
    $extended = preg_replace('/^[\s]*(.*)[\s]*$/', '\\1', $extended);

    return array('main' => $main, 'extended' => $extended);
}

/**
 * get_post() - Retrieves post data given a post ID or post object.
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5.1
 * @uses $wpdb
 * @link http://codex.wordpress.org/Function_Reference/get_post
 *
 * @param int|object &$post post ID or post object
 * @param string $output {@internal Missing Description}}
 * @param string $filter {@internal Missing Description}}
 * @return mixed {@internal Missing Description}}
 */
function &get_post(&$post, $output = OBJECT, $filter = 'raw') {
    global $wpdb;
    $null = null;

    if ( empty($post) ) {
        if ( isset($GLOBALS['post']) )
            $_post = & $GLOBALS['post'];
        else
            return $null;
    } elseif ( is_object($post) ) {
        _get_post_ancestors($post);
        wp_cache_add($post->ID, $post, 'posts');
        $_post = &$post;
    } else {
        $post = (int) $post;
        if ( ! $_post = wp_cache_get($post, 'posts') ) {
            $_post = & $wpdb->get_row($wpdb->prepare("SELECT * FROM $wpdb->posts WHERE ID = %d LIMIT 1", $post));
            if ( ! $_post )
                return $null;
            _get_post_ancestors($_post);
            wp_cache_add($_post->ID, $_post, 'posts');
        }
    }

    $_post = sanitize_post($_post, $filter);

    if ( $output == OBJECT ) {
        return $_post;
    } elseif ( $output == ARRAY_A ) {
        $__post = get_object_vars($_post);
        return $__post;
    } elseif ( $output == ARRAY_N ) {
        $__post = array_values(get_object_vars($_post));
        return $__post;
    } else {
        return $_post;
    }
}

/**
 * Retrieve ancestors of a post.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.5
 *
 * @param int|object $post Post ID or post object
 * @return array Ancestor IDs or empty array if none are found.
 */
function get_post_ancestors($post) {
    $post = get_post($post);

    if ( !empty($post->ancestors) )
        return $post->ancestors;

    return array();
}

/**
 * Retrieve data from a post field based on Post ID.
 *
 * Examples of the post field will be, 'post_type', 'post_status', 'content',
 * etc and based off of the post object property or key names.
 *
 * The context values are based off of the taxonomy filter functions and
 * supported values are found within those functions.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 * @uses sanitize_post_field() See for possible $context values.
 *
 * @param string $field Post field name
 * @param id $post Post ID
 * @param string $context Optional. How to filter the field. Default is display.
 * @return WP_Error|string Value in post field or WP_Error on failure
 */
function get_post_field( $field, $post, $context = 'display' ) {
    $post = (int) $post;
    $post = get_post( $post );

    if ( is_wp_error($post) )
        return $post;

    if ( !is_object($post) )
        return '';

    if ( !isset($post->$field) )
        return '';

    return sanitize_post_field($field, $post->$field, $post->ID, $context);
}

/**
 * Retrieve the mime type of an attachment based on the ID.
 *
 * This function can be used with any post type, but it makes more sense with
 * attachments.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.0
 *
 * @param int $ID Optional. Post ID.
 * @return bool|string False on failure or returns the mime type
 */
function get_post_mime_type($ID = '') {
    $post = & get_post($ID);

    if ( is_object($post) )
        return $post->post_mime_type;

    return false;
}

/**
 * Retrieve the post status based on the Post ID.
 *
 * If the post ID is of an attachment, then the parent post status will be given
 * instead.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.0
 *
 * @param int $ID Post ID
 * @return string|bool Post status or false on failure.
 */
function get_post_status($ID = '') {
    $post = get_post($ID);

    if ( is_object($post) ) {
        if ( ('attachment' == $post->post_type) && $post->post_parent && ($post->ID != $post->post_parent) )
            return get_post_status($post->post_parent);
        else
            return $post->post_status;
    }

    return false;
}

/**
 * Retrieve all of the WordPress supported post statuses.
 *
 * Posts have a limited set of valid status values, this provides the
 * post_status values and descriptions.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.5
 *
 * @return array List of post statuses.
 */
function get_post_statuses( ) {
    $status = array(
        'draft'            => __('Draft'),
        'pending'        => __('Pending Review'),
        'private'        => __('Private'),
        'publish'        => __('Published')
    );

    return $status;
}

/**
 * Retrieve all of the WordPress support page statuses.
 *
 * Pages have a limited set of valid status values, this provides the
 * post_status values and descriptions.
 *
 * @package WordPress
 * @subpackage Page
 * @since 2.5
 *
 * @return array List of page statuses.
 */
function get_page_statuses( ) {
    $status = array(
        'draft'            => __('Draft'),
        'private'        => __('Private'),
        'publish'        => __('Published')
    );

    return $status;
}

/**
 * get_post_type() - Returns post type
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @uses $wpdb
 * @uses $posts {@internal Missing Description}}
 *
 * @param mixed $post post object or post ID
 * @return mixed post type or false
 */
function get_post_type($post = false) {
    global $posts;

    if ( false === $post )
        $post = $posts[0];
    elseif ( (int) $post )
        $post = get_post($post, OBJECT);

    if ( is_object($post) )
        return $post->post_type;

    return false;
}

/**
 * set_post_type() - Set post type
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.5
 *
 * @uses $wpdb
 * @uses $posts {@internal Missing Description}}
 *
 * @param mixed $post_id post ID
 * @param mixed post type
 * @return bool {@internal Missing Description}}
 */
function set_post_type( $post_id = 0, $post_type = 'post' ) {
    global $wpdb;

    $post_type = sanitize_post_field('post_type', $post_type, $post_id, 'db');
    $return = $wpdb->query( $wpdb->prepare("UPDATE $wpdb->posts SET post_type = %s WHERE ID = %d", $post_type, $post_id) );

    if ( 'page' == $post_type )
        clean_page_cache($post_id);
    else
        clean_post_cache($post_id);

    return $return;
}

/**
 * get_posts() - Returns a number of posts
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.2
 * @uses $wpdb
 * @link http://codex.wordpress.org/Template_Tags/get_posts
 *
 * @param array $args {@internal Missing Description}}
 * @return array {@internal Missing Description}}
 */
function get_posts($args = null) {
    $defaults = array(
        'numberposts' => 5, 'offset' => 0,
        'category' => 0, 'orderby' => 'post_date',
        'order' => 'DESC', 'include' => '',
        'exclude' => '', 'meta_key' => '',
        'meta_value' =>'', 'post_type' => 'post',
        'post_parent' => 0
    );

    $r = wp_parse_args( $args, $defaults );
    if ( empty( $r['post_status'] ) )
        $r['post_status'] = ( 'attachment' == $r['post_type'] ) ? 'inherit' : 'publish';
    if ( ! empty($r['numberposts']) )
        $r['posts_per_page'] = $r['numberposts'];
    if ( ! empty($r['category']) )
        $r['cat'] = $r['category'];
    if ( ! empty($r['include']) ) {
        $incposts = preg_split('/[\s,]+/',$r['include']);
        $r['posts_per_page'] = count($incposts);  // only the number of posts included
        $r['post__in'] = $incposts;
    } elseif ( ! empty($r['exclude']) )
        $r['post__not_in'] = preg_split('/[\s,]+/',$r['exclude']);

    $get_posts = new WP_Query;
    return $get_posts->query($r);

}

//
// Post meta functions
//

/**
 * add_post_meta() - adds metadata for post
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 * @uses $wpdb
 * @link http://codex.wordpress.org/Function_Reference/add_post_meta
 *
 * @param int $post_id post ID
 * @param string $key {@internal Missing Description}}
 * @param mixed $value {@internal Missing Description}}
 * @param bool $unique whether to check for a value with the same key
 * @return bool {@internal Missing Description}}
 */
function add_post_meta($post_id, $meta_key, $meta_value, $unique = false) {
    global $wpdb;

    // make sure meta is added to the post, not a revision
    if ( $the_post = wp_is_post_revision($post_id) )
        $post_id = $the_post;

    // expected_slashed ($meta_key)
    $meta_key = stripslashes($meta_key);

    if ( $unique && $wpdb->get_var( $wpdb->prepare( "SELECT meta_key FROM $wpdb->postmeta WHERE meta_key = %s AND post_id = %d", $meta_key, $post_id ) ) )
        return false;

    $meta_value = maybe_serialize($meta_value);

    $wpdb->insert( $wpdb->postmeta, compact( 'post_id', 'meta_key', 'meta_value' ) );

    wp_cache_delete($post_id, 'post_meta');

    return true;
}

/**
 * delete_post_meta() - delete post metadata
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 * @uses $wpdb
 * @link http://codex.wordpress.org/Function_Reference/delete_post_meta
 *
 * @param int $post_id post ID
 * @param string $key {@internal Missing Description}}
 * @param mixed $value {@internal Missing Description}}
 * @return bool {@internal Missing Description}}
 */
function delete_post_meta($post_id, $key, $value = '') {
    global $wpdb;

    $post_id = absint( $post_id );

    // expected_slashed ($key, $value)
    $key = stripslashes( $key );
    $value = stripslashes( $value );

    if ( empty( $value ) )
        $meta_id = $wpdb->get_var( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = %s", $post_id, $key ) );
    else
        $meta_id = $wpdb->get_var( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = %s AND meta_value = %s", $post_id, $key, $value ) );

    if ( !$meta_id )
        return false;

    if ( empty( $value ) )
        $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = %s", $post_id, $key ) );
    else
        $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->postmeta WHERE post_id = %d AND meta_key = %s AND meta_value = %s", $post_id, $key, $value ) );

    wp_cache_delete($post_id, 'post_meta');

    return true;
}

/**
 * get_post_meta() - Get a post meta field
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 * @uses $wpdb
 * @link http://codex.wordpress.org/Function_Reference/get_post_meta
 *
 * @param int $post_id post ID
 * @param string $key The meta key to retrieve
 * @param bool $single Whether to return a single value
 * @return mixed {@internal Missing Description}}
 */
function get_post_meta($post_id, $key, $single = false) {
    $post_id = (int) $post_id;

    $meta_cache = wp_cache_get($post_id, 'post_meta');

    if ( isset($meta_cache[$key]) ) {
        if ( $single ) {
            return maybe_unserialize( $meta_cache[$key][0] );
        } else {
            return maybe_unserialize( $meta_cache[$key] );
        }
    }

    if ( !$meta_cache ) {
        update_postmeta_cache($post_id);
        $meta_cache = wp_cache_get($post_id, 'post_meta');
    }

    if ( $single ) {
        if ( isset($meta_cache[$key][0]) )
            return maybe_unserialize($meta_cache[$key][0]);
        else
            return '';
    } else {
        return maybe_unserialize($meta_cache[$key]);
    }
}

/**
 * update_post_meta() - Update a post meta field
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 * @uses $wpdb
 * @link http://codex.wordpress.org/Function_Reference/update_post_meta
 *
 * @param int $post_id post ID
 * @param string $key {@internal Missing Description}}
 * @param mixed $value {@internal Missing Description}}
 * @param mixed $prev_value previous value (for differentiating between meta fields with the same key and post ID)
 * @return bool {@internal Missing Description}}
 */
function update_post_meta($post_id, $meta_key, $meta_value, $prev_value = '') {
    global $wpdb;

    // expected_slashed ($meta_key)
    $meta_key = stripslashes($meta_key);

    if ( ! $wpdb->get_var( $wpdb->prepare( "SELECT meta_key FROM $wpdb->postmeta WHERE meta_key = %s AND post_id = %d", $meta_key, $post_id ) ) ) {
        return add_post_meta($post_id, $meta_key, $meta_value);
    }

    $meta_value = maybe_serialize($meta_value);

    $data  = compact( 'meta_value' );
    $where = compact( 'meta_key', 'post_id' );

    if ( !empty( $prev_value ) ) {
        $prev_value = maybe_serialize($prev_value);
        $where['meta_value'] = $prev_value;
    }

    $wpdb->update( $wpdb->postmeta, $data, $where );
    wp_cache_delete($post_id, 'post_meta');
    return true;
}

/**
 * delete_post_meta_by_key() - Delete everything from post meta matching $post_meta_key
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 * @uses $wpdb
 *
 * @param string $post_meta_key What to search for when deleting
 * @return bool Whether the post meta key was deleted from the database
 */
function delete_post_meta_by_key($post_meta_key) {
    global $wpdb;
    if ( $wpdb->query($wpdb->prepare("DELETE FROM $wpdb->postmeta WHERE meta_key = %s", $post_meta_key)) ) {
        /** @todo Get post_ids and delete cache */
        // wp_cache_delete($post_id, 'post_meta');
        return true;
    }
    return false;
}

/**
 * get_post_custom() - Retrieve post custom fields
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.2
 * @link http://codex.wordpress.org/Function_Reference/get_post_custom
 *
 * @uses $id
 * @uses $wpdb
 *
 * @param int $post_id post ID
 * @return array {@internal Missing Description}}
 */
function get_post_custom($post_id = 0) {
    global $id;

    if ( !$post_id )
        $post_id = (int) $id;

    $post_id = (int) $post_id;

    if ( ! wp_cache_get($post_id, 'post_meta') )
        update_postmeta_cache($post_id);

    return wp_cache_get($post_id, 'post_meta');
}

/**
 * get_post_custom_keys() - Retrieve post custom field names
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.2
 * @link http://codex.wordpress.org/Function_Reference/get_post_custom_keys
 *
 * @param int $post_id post ID
 * @return array|null Either array of the keys, or null if keys would not be retrieved
 */
function get_post_custom_keys( $post_id = 0 ) {
    $custom = get_post_custom( $post_id );

    if ( !is_array($custom) )
        return;

    if ( $keys = array_keys($custom) )
        return $keys;
}

/**
 * get_post_custom_values() - Retrieve values for a custom post field
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.2
 * @link http://codex.wordpress.org/Function_Reference/get_post_custom_values
 *
 * @param string $key field name
 * @param int $post_id post ID
 * @return mixed {@internal Missing Description}}
 */
function get_post_custom_values( $key = '', $post_id = 0 ) {
    $custom = get_post_custom($post_id);

    return $custom[$key];
}

/**
 * sanitize_post() - Sanitize every post field
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 *
 * @param object|array $post The Post Object or Array
 * @param string $context How to sanitize post fields
 * @return object|array The now sanitized Post Object or Array (will be the same type as $post)
 */
function sanitize_post($post, $context = 'display') {
    if ( 'raw' == $context )
        return $post;
    if ( is_object($post) ) {
        foreach ( array_keys(get_object_vars($post)) as $field )
            $post->$field = sanitize_post_field($field, $post->$field, $post->ID, $context);
    } else {
        foreach ( array_keys($post) as $field )
            $post[$field] = sanitize_post_field($field, $post[$field], $post['ID'], $context);
    }
    return $post;
}

/**
 * sanitize_post_field() - Sanitize post field based on context
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 *
 * @param string $field The Post Object field name
 * @param string $value The Post Object value
 * @param int $postid Post ID
 * @param string $context How to sanitize post fields
 * @return string Sanitized value
 */
function sanitize_post_field($field, $value, $post_id, $context) {
    $int_fields = array('ID', 'post_parent', 'menu_order');
    if ( in_array($field, $int_fields) )
        $value = (int) $value;

    if ( 'raw' == $context )
        return $value;

    $prefixed = false;
    if ( false !== strpos($field, 'post_') ) {
        $prefixed = true;
        $field_no_prefix = str_replace('post_', '', $field);
    }

    if ( 'edit' == $context ) {
        $format_to_edit = array('post_content', 'post_excerpt', 'post_title', 'post_password');

        if ( $prefixed ) {
            $value = apply_filters("edit_$field", $value, $post_id);
            // Old school
            $value = apply_filters("${field_no_prefix}_edit_pre", $value, $post_id);
        } else {
            $value = apply_filters("edit_post_$field", $value, $post_id);
        }

        if ( in_array($field, $format_to_edit) ) {
            if ( 'post_content' == $field )
                $value = format_to_edit($value, user_can_richedit());
            else
                $value = format_to_edit($value);
        } else {
            $value = attribute_escape($value);
        }
    } else if ( 'db' == $context ) {
        if ( $prefixed ) {
            $value = apply_filters("pre_$field", $value);
            $value = apply_filters("${field_no_prefix}_save_pre", $value);
        } else {
            $value = apply_filters("pre_post_$field", $value);
            $value = apply_filters("${field}_pre", $value);
        }
    } else {
        // Use display filters by default.
        if ( $prefixed )
            $value = apply_filters($field, $value, $post_id, $context);
        else
            $value = apply_filters("post_$field", $value, $post_id, $context);
    }

    if ( 'attribute' == $context )
        $value = attribute_escape($value);
    else if ( 'js' == $context )
        $value = js_escape($value);

    return $value;
}

/**
 * Count number of posts of a post type and is user has permissions to view.
 *
 * This function provides an efficient method of finding the amount of post's
 * type a blog has. Another method is to count the amount of items in
 * get_posts(), but that method has a lot of overhead with doing so. Therefore,
 * when developing for 2.5+, use this function instead.
 *
 * The $perm parameter checks for 'readable' value and if the user can read
 * private posts, it will display that for the user that is signed in.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.5
 * @link http://codex.wordpress.org/Template_Tags/wp_count_posts
 *
 * @param string $type Optional. Post type to retrieve count
 * @param string $perm Optional. 'readable' or empty.
 * @return object Number of posts for each status
 */
function wp_count_posts( $type = 'post', $perm = '' ) {
    global $wpdb;

    $user = wp_get_current_user();

    $cache_key = $type;

    $query = "SELECT post_status, COUNT( * ) AS num_posts FROM {$wpdb->posts} WHERE post_type = %s";
    if ( 'readable' == $perm && is_user_logged_in() ) {
        if ( !current_user_can("read_private_{$type}s") ) {
            $cache_key .= '_' . $perm . '_' . $user->ID;
            $query .= " AND (post_status != 'private' OR ( post_author = '$user->ID' AND post_status = 'private' ))";
        }
    }
    $query .= ' GROUP BY post_status';

    $count = wp_cache_get($cache_key, 'counts');
    if ( false !== $count )
        return $count;

    $count = $wpdb->get_results( $wpdb->prepare( $query, $type ), ARRAY_A );

    $stats = array( );
    foreach( (array) $count as $row_num => $row ) {
        $stats[$row['post_status']] = $row['num_posts'];
    }

    $stats = (object) $stats;
    wp_cache_set($cache_key, $stats, 'counts');

    return $stats;
}


/**
 * wp_count_attachments() - Count number of attachments
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.5
 *
 * @param string|array $post_mime_type Array or comma-separated list of MIME patterns
 * @return array Number of posts for each post_mime_type
 */

function wp_count_attachments( $mime_type = '' ) {
    global $wpdb;

    $and = wp_post_mime_type_where( $mime_type );
    $count = $wpdb->get_results( "SELECT post_mime_type, COUNT( * ) AS num_posts FROM $wpdb->posts WHERE post_type = 'attachment' $and GROUP BY post_mime_type", ARRAY_A );

    $stats = array( );
    foreach( (array) $count as $row ) {
        $stats[$row['post_mime_type']] = $row['num_posts'];
    }

    return (object) $stats;
}

/**
 * wp_match_mime_type() - Check a MIME-Type against a list
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.5
 *
 * @param string|array $wildcard_mime_types e.g. audio/mpeg or image (same as image/*) or flash (same as *flash*)
 * @param string|array $real_mime_types post_mime_type values
 * @return array array(wildcard=>array(real types))
 */
function wp_match_mime_types($wildcard_mime_types, $real_mime_types) {
    $matches = array();
    if ( is_string($wildcard_mime_types) )
        $wildcard_mime_types = array_map('trim', explode(',', $wildcard_mime_types));
    if ( is_string($real_mime_types) )
        $real_mime_types = array_map('trim', explode(',', $real_mime_types));
    $wild = '[-._a-z0-9]*';
    foreach ( (array) $wildcard_mime_types as $type ) {
        $type = str_replace('*', $wild, $type);
        $patternses[1][$type] = "^$type$";
        if ( false === strpos($type, '/') ) {
            $patternses[2][$type] = "^$type/";
            $patternses[3][$type] = $type;
        }
    }
    asort($patternses);
    foreach ( $patternses as $patterns )
        foreach ( $patterns as $type => $pattern )
            foreach ( (array) $real_mime_types as $real )
                if ( preg_match("#$pattern#", $real) && ( empty($matches[$type]) || false === array_search($real, $matches[$type]) ) )
                    $matches[$type][] = $real;
    return $matches;
}

/**
 * wp_get_post_mime_type_where() - Convert MIME types into SQL
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.5
 *
 * @param string|array $mime_types MIME types
 * @return string SQL AND clause
 */
function wp_post_mime_type_where($post_mime_types) {
    $where = '';
    $wildcards = array('', '%', '%/%');
    if ( is_string($post_mime_types) )
        $post_mime_types = array_map('trim', explode(',', $post_mime_types));
    foreach ( (array) $post_mime_types as $mime_type ) {
        $mime_type = preg_replace('/\s/', '', $mime_type);
        $slashpos = strpos($mime_type, '/');
        if ( false !== $slashpos ) {
            $mime_group = preg_replace('/[^-*.a-zA-Z0-9]/', '', substr($mime_type, 0, $slashpos));
            $mime_subgroup = preg_replace('/[^-*.a-zA-Z0-9]/', '', substr($mime_type, $slashpos + 1));
            if ( empty($mime_subgroup) )
                $mime_subgroup = '*';
            else
                $mime_subgroup = str_replace('/', '', $mime_subgroup);
            $mime_pattern = "$mime_group/$mime_subgroup";
        } else {
            $mime_pattern = preg_replace('/[^-*.a-zA-Z0-9]/', '', $mime_type);
            if ( false === strpos($mime_pattern, '*') )
                $mime_pattern .= '/*';
        }

        $mime_pattern = preg_replace('/\*+/', '%', $mime_pattern);

        if ( in_array( $mime_type, $wildcards ) )
            return '';

        if ( false !== strpos($mime_pattern, '%') )
            $wheres[] = "post_mime_type LIKE '$mime_pattern'";
        else
            $wheres[] = "post_mime_type = '$mime_pattern'";
    }
    if ( !empty($wheres) )
        $where = ' AND (' . join(' OR ', $wheres) . ') ';
    return $where;
}

/**
 * wp_delete_post() - Deletes a Post
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.0.0
 *
 * @param int $postid post ID
 * @return mixed {@internal Missing Description}}
 */
function wp_delete_post($postid = 0) {
    global $wpdb, $wp_rewrite;

    if ( !$post = $wpdb->get_row($wpdb->prepare("SELECT * FROM $wpdb->posts WHERE ID = %d", $postid)) )
        return $post;

    if ( 'attachment' == $post->post_type )
        return wp_delete_attachment($postid);

    do_action('delete_post', $postid);

    /** @todo delete for pluggable post taxonomies too */
    wp_delete_object_term_relationships($postid, array('category', 'post_tag'));

    $parent_data = array( 'post_parent' => $post->post_parent );
    $parent_where = array( 'post_parent' => $postid );

    if ( 'page' == $post->post_type) {
         // if the page is defined in option page_on_front or post_for_posts,
        // adjust the corresponding options
        if ( get_option('page_on_front') == $postid ) {
            update_option('show_on_front', 'posts');
            delete_option('page_on_front');
        }
        if ( get_option('page_for_posts') == $postid ) {
            delete_option('page_for_posts');
        }

        // Point children of this page to its parent, also clean the cache of affected children
        $children_query = $wpdb->prepare("SELECT * FROM $wpdb->posts WHERE post_parent = %d AND post_type='page'", $postid);
        $children = $wpdb->get_results($children_query);

        $wpdb->update( $wpdb->posts, $parent_data, $parent_where + array( 'post_type' => 'page' ) );
    }

    // Do raw query.  wp_get_post_revisions() is filtered
    $revision_ids = $wpdb->get_col( $wpdb->prepare( "SELECT ID FROM $wpdb->posts WHERE post_parent = %d AND post_type = 'revision'", $postid ) );
    // Use wp_delete_post (via wp_delete_post_revision) again.  Ensures any meta/misplaced data gets cleaned up.
    foreach ( $revision_ids as $revision_id )
        wp_delete_post_revision( $revision_id );

    // Point all attachments to this post up one level
    $wpdb->update( $wpdb->posts, $parent_data, $parent_where + array( 'post_type' => 'attachment' ) );

    $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->posts WHERE ID = %d", $postid ));

    $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->comments WHERE comment_post_ID = %d", $postid ));

    $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->postmeta WHERE post_id = %d", $postid ));

    if ( 'page' == $post->post_type ) {
        clean_page_cache($postid);

        foreach ( (array) $children as $child )
            clean_page_cache($child->ID);

        $wp_rewrite->flush_rules();
    } else {
        clean_post_cache($postid);
    }

    do_action('deleted_post', $postid);

    return $post;
}

/**
 * wp_get_post_categories() - Retrieve the list of categories for a post
 *
 * Compatibility layer for themes and plugins. Also an easy layer of abstraction
 * away from the complexity of the taxonomy layer.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @uses wp_get_object_terms() Retrieves the categories. Args details can be found here
 *
 * @param int $post_id Optional. The Post ID
 * @param array $args Optional. Overwrite the defaults
 * @return array {@internal Missing Description}}
 */
function wp_get_post_categories( $post_id = 0, $args = array() ) {
    $post_id = (int) $post_id;

    $defaults = array('fields' => 'ids');
    $args = wp_parse_args( $args, $defaults );

    $cats = wp_get_object_terms($post_id, 'category', $args);
    return $cats;
}

/**
 * wp_get_post_tags() - Retrieve the post tags
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 *
 * @uses wp_get_object_terms() Gets the tags for returning. Args can be found here
 *
 * @param int $post_id Optional. The Post ID
 * @param array $args Optional. Overwrite the defaults
 * @return mixed The tags the post has currently
 */
function wp_get_post_tags( $post_id = 0, $args = array() ) {
    $post_id = (int) $post_id;

    $defaults = array('fields' => 'all');
    $args = wp_parse_args( $args, $defaults );

    $tags = wp_get_object_terms($post_id, 'post_tag', $args);

    return $tags;
}

/**
 * wp_get_recent_posts() - Get the $num most recent posts
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.0.0
 *
 * @param int $num number of posts to get
 * @return array {@internal Missing Description}}
 */
function wp_get_recent_posts($num = 10) {
    global $wpdb;

    // Set the limit clause, if we got a limit
    $num = (int) $num;
    if ($num) {
        $limit = "LIMIT $num";
    }

    $sql = "SELECT * FROM $wpdb->posts WHERE post_type = 'post' ORDER BY post_date DESC $limit";
    $result = $wpdb->get_results($sql,ARRAY_A);

    return $result?$result:array();
}

/**
 * wp_get_single_post() - Get one post
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.0.0
 * @uses $wpdb
 *
 * @param int $postid post ID
 * @param string $mode How to return result, either OBJECT, ARRAY_N, or ARRAY_A
 * @return object|array Post object or array holding post contents and information
 */
function wp_get_single_post($postid = 0, $mode = OBJECT) {
    $postid = (int) $postid;

    $post = get_post($postid, $mode);

    // Set categories and tags
    if($mode == OBJECT) {
        $post->post_category = wp_get_post_categories($postid);
        $post->tags_input = wp_get_post_tags($postid, array('fields' => 'names'));
    }
    else {
        $post['post_category'] = wp_get_post_categories($postid);
        $post['tags_input'] = wp_get_post_tags($postid, array('fields' => 'names'));
    }

    return $post;
}

/**
 * wp_insert_post() - Insert a post
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.0.0
 *
 * @uses $wpdb
 * @uses $wp_rewrite
 * @uses $user_ID
 * @uses $allowedtags
 *
 * @param array $postarr post contents
 * @return int post ID or 0 on error
 */
function wp_insert_post($postarr = array(), $wp_error = false) {
    global $wpdb, $wp_rewrite, $user_ID;

    $defaults = array('post_status' => 'draft', 'post_type' => 'post', 'post_author' => $user_ID,
        'ping_status' => get_option('default_ping_status'), 'post_parent' => 0,
        'menu_order' => 0, 'to_ping' =>  '', 'pinged' => '', 'post_password' => '',
        'guid' => '', 'post_content_filtered' => '', 'post_excerpt' => '');

    $postarr = wp_parse_args($postarr, $defaults);
    $postarr = sanitize_post($postarr, 'db');

    // export array as variables
    extract($postarr, EXTR_SKIP);

    // Are we updating or creating?
    $update = false;
    if ( !empty($ID) ) {
        $update = true;
        $previous_status = get_post_field('post_status', $ID);
    } else {
        $previous_status = 'new';
    }

    if ( ('' == $post_content) && ('' == $post_title) && ('' == $post_excerpt) ) {
        if ( $wp_error )
            return new WP_Error('empty_content', __('Content, title, and excerpt are empty.'));
        else
            return 0;
    }

    // Make sure we set a valid category
    if (0 == count($post_category) || !is_array($post_category)) {
        $post_category = array(get_option('default_category'));
    }

    if ( empty($post_author) )
        $post_author = $user_ID;

    if ( empty($post_status) )
        $post_status = 'draft';

    if ( empty($post_type) )
        $post_type = 'post';

    // Get the post ID and GUID
    if ( $update ) {
        $post_ID = (int) $ID;
        $guid = get_post_field( 'guid', $post_ID );
    }

    // Create a valid post name.  Drafts are allowed to have an empty
    // post name.
    if ( empty($post_name) ) {
        if ( 'draft' != $post_status )
            $post_name = sanitize_title($post_title);
    } else {
        $post_name = sanitize_title($post_name);
    }

    // If the post date is empty (due to having been new or a draft) and status is not 'draft', set date to now
    if ( empty($post_date) || '0000-00-00 00:00:00' == $post_date ) {
        if ( !in_array($post_status, array('draft', 'pending')) )
            $post_date = current_time('mysql');
        else
            $post_date = '0000-00-00 00:00:00';
    }

    if ( empty($post_date_gmt) || '0000-00-00 00:00:00' == $post_date_gmt ) {
        if ( !in_array($post_status, array('draft', 'pending')) )
            $post_date_gmt = get_gmt_from_date($post_date);
        else
            $post_date_gmt = '0000-00-00 00:00:00';
    }

    if ( $update || '0000-00-00 00:00:00' == $post_date ) {
        $post_modified     = current_time( 'mysql' );
        $post_modified_gmt = current_time( 'mysql', 1 );
    } else {
        $post_modified     = $post_date;
        $post_modified_gmt = $post_date_gmt;
    }

    if ( 'publish' == $post_status ) {
        $now = gmdate('Y-m-d H:i:59');
        if ( mysql2date('U', $post_date_gmt) > mysql2date('U', $now) )
            $post_status = 'future';
    }

    if ( empty($comment_status) ) {
        if ( $update )
            $comment_status = 'closed';
        else
            $comment_status = get_option('default_comment_status');
    }
    if ( empty($ping_status) )
        $ping_status = get_option('default_ping_status');

    if ( isset($to_ping) )
        $to_ping = preg_replace('|\s+|', "\n", $to_ping);
    else
        $to_ping = '';

    if ( ! isset($pinged) )
        $pinged = '';

    if ( isset($post_parent) )
        $post_parent = (int) $post_parent;
    else
        $post_parent = 0;

    if ( isset($menu_order) )
        $menu_order = (int) $menu_order;
    else
        $menu_order = 0;

    if ( !isset($post_password) )
        $post_password = '';

    if ( 'draft' != $post_status ) {
        $post_name_check = $wpdb->get_var($wpdb->prepare("SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type = %s AND ID != %d AND post_parent = %d LIMIT 1", $post_name, $post_type, $post_ID, $post_parent));

        if ($post_name_check || in_array($post_name, $wp_rewrite->feeds) ) {
            $suffix = 2;
            do {
                $alt_post_name = substr($post_name, 0, 200-(strlen($suffix)+1)). "-$suffix";
                $post_name_check = $wpdb->get_var($wpdb->prepare("SELECT post_name FROM $wpdb->posts WHERE post_name = %s AND post_type = %s AND ID != %d AND post_parent = %d LIMIT 1", $alt_post_name, $post_type, $post_ID, $post_parent));
                $suffix++;
            } while ($post_name_check);
            $post_name = $alt_post_name;
        }
    }

    // expected_slashed (everything!)
    $data = compact( array( 'post_author', 'post_date', 'post_date_gmt', 'post_content', 'post_content_filtered', 'post_title', 'post_excerpt', 'post_status', 'post_type', 'comment_status', 'ping_status', 'post_password', 'post_name', 'to_ping', 'pinged', 'post_modified', 'post_modified_gmt', 'post_parent', 'menu_order', 'guid' ) );
    $data = stripslashes_deep( $data );
    $where = array( 'ID' => $post_ID );

    if ($update) {
        do_action( 'pre_post_update', $post_ID );
        if ( false === $wpdb->update( $wpdb->posts, $data, $where ) ) {
            if ( $wp_error )
                return new WP_Error('db_update_error', __('Could not update post in the database'), $wpdb->last_error);
            else
                return 0;
        }
    } else {
        $data['post_mime_type'] = stripslashes( $post_mime_type ); // This isn't in the update
        if ( false === $wpdb->insert( $wpdb->posts, $data ) ) {
            if ( $wp_error )
                return new WP_Error('db_insert_error', __('Could not insert post into the database'), $wpdb->last_error);
            else
                return 0;
        }
        $post_ID = (int) $wpdb->insert_id;

        // use the newly generated $post_ID
        $where = array( 'ID' => $post_ID );
    }

    if ( empty($post_name) && 'draft' != $post_status ) {
        $post_name = sanitize_title($post_title, $post_ID);
        $wpdb->update( $wpdb->posts, compact( 'post_name' ), $where );
    }

    wp_set_post_categories( $post_ID, $post_category );
    wp_set_post_tags( $post_ID, $tags_input );

    $current_guid = get_post_field( 'guid', $post_ID );

    if ( 'page' == $post_type )
        clean_page_cache($post_ID);
    else
        clean_post_cache($post_ID);

    // Set GUID
    if ( !$update && '' == $current_guid )
        $wpdb->update( $wpdb->posts, array( 'guid' => get_permalink( $post_ID ) ), $where );

    $post = get_post($post_ID);

    if ( !empty($page_template) && 'page' == $post_type ) {
        $post->page_template = $page_template;
        $page_templates = get_page_templates();
        if ( 'default' != $page_template && !in_array($page_template, $page_templates) ) {
            if ( $wp_error )
                return new WP_Error('invalid_page_template', __('The page template is invalid.'));
            else
                return 0;
        }
        update_post_meta($post_ID, '_wp_page_template',  $page_template);
    }

    wp_transition_post_status($post_status, $previous_status, $post);

    if ( $update)
        do_action('edit_post', $post_ID, $post);

    do_action('save_post', $post_ID, $post);
    do_action('wp_insert_post', $post_ID, $post);

    return $post_ID;
}

/**
 * wp_update_post() - Update a post
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.0.0
 * @uses $wpdb
 *
 * @param array $postarr post data
 * @return int {@internal Missing Description}}
 */
function wp_update_post($postarr = array()) {
    if ( is_object($postarr) )
        $postarr = get_object_vars($postarr);

    // First, get all of the original fields
    $post = wp_get_single_post($postarr['ID'], ARRAY_A);

    // Escape data pulled from DB.
    $post = add_magic_quotes($post);

    // Passed post category list overwrites existing category list if not empty.
    if ( isset($postarr['post_category']) && is_array($postarr['post_category'])
             && 0 != count($postarr['post_category']) )
        $post_cats = $postarr['post_category'];
    else
        $post_cats = $post['post_category'];

    // Drafts shouldn't be assigned a date unless explicitly done so by the user
    if ( in_array($post['post_status'], array('draft', 'pending')) && empty($postarr['edit_date']) && empty($postarr['post_date']) &&
             ('0000-00-00 00:00:00' == $post['post_date']) )
        $clear_date = true;
    else
        $clear_date = false;

    // Merge old and new fields with new fields overwriting old ones.
    $postarr = array_merge($post, $postarr);
    $postarr['post_category'] = $post_cats;
    if ( $clear_date ) {
        $postarr['post_date'] = '';
        $postarr['post_date_gmt'] = '';
    }

    if ($postarr['post_type'] == 'attachment')
        return wp_insert_attachment($postarr);

    return wp_insert_post($postarr);
}

/**
 * wp_publish_post() - Mark a post as "published"
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 * @uses $wpdb
 *
 * @param int $post_id Post ID
 * @return int|null {@internal Missing Description}}
 */
function wp_publish_post($post_id) {
    global $wpdb;

    $post = get_post($post_id);

    if ( empty($post) )
        return;

    if ( 'publish' == $post->post_status )
        return;

    $wpdb->update( $wpdb->posts, array( 'post_status' => 'publish' ), array( 'ID' => $post_id ) );

    $old_status = $post->post_status;
    $post->post_status = 'publish';
    wp_transition_post_status('publish', $old_status, $post);

    // Update counts for the post's terms.
    foreach ( get_object_taxonomies('post') as $taxonomy ) {
        $terms = wp_get_object_terms($post_id, $taxonomy, 'fields=tt_ids');
        wp_update_term_count($terms, $taxonomy);
    }

    do_action('edit_post', $post_id, $post);
    do_action('save_post', $post_id, $post);
    do_action('wp_insert_post', $post_id, $post);
}

/**
 * check_and_publish_future_post() - check to make sure post has correct status before
 * passing it on to be published. Invoked by cron 'publish_future_post' event
 * This safeguard prevents cron from publishing drafts, etc.
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.5
 * @uses $wpdb
 *
 * @param int $post_id Post ID
 * @return int|null {@internal Missing Description}}
 */
function check_and_publish_future_post($post_id) {

    $post = get_post($post_id);

    if ( empty($post) )
        return;

    if ( 'future' != $post->post_status )
        return;

    return wp_publish_post($post_id);
}

/**
 * wp_add_post_tags() - Adds the tags to a post
 *
 * @uses wp_set_post_tags() Same first two paraeters, but the last parameter is always set to true.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 *
 * @param int $post_id Optional. Post ID
 * @param string $tags The tags to set for the post
 * @return bool|null Will return false if $post_id is not an integer or is 0. Will return null otherwise
 */
function wp_add_post_tags($post_id = 0, $tags = '') {
    return wp_set_post_tags($post_id, $tags, true);
}

/**
 * wp_set_post_tags() - Set the tags for a post
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 * @uses $wpdb
 *
 * @param int $post_id post ID
 * @param string $tags The tags to set for the post
 * @param bool $append If true, don't delete existing tags, just add on. If false, replace the tags with the new tags.
 * @return bool|null Will return false if $post_id is not an integer or is 0. Will return null otherwise
 */
function wp_set_post_tags( $post_id = 0, $tags = '', $append = false ) {

    $post_id = (int) $post_id;

    if ( !$post_id )
        return false;

    if ( empty($tags) )
        $tags = array();
    $tags = (is_array($tags)) ? $tags : explode( ',', trim($tags, " \n\t\r\0\x0B,") );
    wp_set_object_terms($post_id, $tags, 'post_tag', $append);
}

/**
 * wp_set_post_categories() - Set categories for a post
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 * @uses $wpdb
 *
 * @param int $post_ID post ID
 * @param array $post_categories
 * @return bool|mixed {@internal Missing Description}}
 */
function wp_set_post_categories($post_ID = 0, $post_categories = array()) {
    $post_ID = (int) $post_ID;
    // If $post_categories isn't already an array, make it one:
    if (!is_array($post_categories) || 0 == count($post_categories) || empty($post_categories))
        $post_categories = array(get_option('default_category'));
    else if ( 1 == count($post_categories) && '' == $post_categories[0] )
        return true;

    $post_categories = array_map('intval', $post_categories);
    $post_categories = array_unique($post_categories);

    return wp_set_object_terms($post_ID, $post_categories, 'category');
}    // wp_set_post_categories()

/**
 * wp_transition_post_status() - Change the post transition status
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 *
 * @param string $new_status {@internal Missing Description}}
 * @param string $old_status {@internal Missing Description}}
 * @param int $post {@internal Missing Description}}
 */
function wp_transition_post_status($new_status, $old_status, $post) {
    if ( $new_status != $old_status ) {
        do_action('transition_post_status', $new_status, $old_status, $post);
        do_action("${old_status}_to_$new_status", $post);
    }
    do_action("${new_status}_$post->post_type", $post->ID, $post);
}

//
// Trackback and ping functions
//

/**
 * add_ping() - Add a URL to those already pung
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 * @uses $wpdb
 *
 * @param int $post_id post ID
 * @param string $uri {@internal Missing Description}}
 * @return mixed {@internal Missing Description}}
 */
function add_ping($post_id, $uri) {
    global $wpdb;
    $pung = $wpdb->get_var( $wpdb->prepare( "SELECT pinged FROM $wpdb->posts WHERE ID = %d", $post_id ));
    $pung = trim($pung);
    $pung = preg_split('/\s/', $pung);
    $pung[] = $uri;
    $new = implode("\n", $pung);
    $new = apply_filters('add_ping', $new);
    // expected_slashed ($new)
    $new = stripslashes($new);
    return $wpdb->update( $wpdb->posts, array( 'pinged' => $new ), array( 'ID' => $post_id ) );
}

/**
 * get_enclosed() - Get enclosures already enclosed for a post
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 * @uses $wpdb
 *
 * @param int $post_id post ID
 * @return array {@internal Missing Description}}
 */
function get_enclosed($post_id) {
    $custom_fields = get_post_custom( $post_id );
    $pung = array();
    if ( !is_array( $custom_fields ) )
        return $pung;

    foreach ( $custom_fields as $key => $val ) {
        if ( 'enclosure' != $key || !is_array( $val ) )
            continue;
        foreach( $val as $enc ) {
            $enclosure = split( "\n", $enc );
            $pung[] = trim( $enclosure[ 0 ] );
        }
    }
    $pung = apply_filters('get_enclosed', $pung);
    return $pung;
}

/**
 * get_pung() - Get URLs already pinged for a post
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 * @uses $wpdb
 *
 * @param int $post_id post ID
 * @return array {@internal Missing Description}}
 */
function get_pung($post_id) {
    global $wpdb;
    $pung = $wpdb->get_var( $wpdb->prepare( "SELECT pinged FROM $wpdb->posts WHERE ID = %d", $post_id ));
    $pung = trim($pung);
    $pung = preg_split('/\s/', $pung);
    $pung = apply_filters('get_pung', $pung);
    return $pung;
}

/**
 * get_to_ping() - Get any URLs in the todo list
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 * @uses $wpdb
 *
 * @param int $post_id post ID
 * @return array {@internal Missing Description}}
 */
function get_to_ping($post_id) {
    global $wpdb;
    $to_ping = $wpdb->get_var( $wpdb->prepare( "SELECT to_ping FROM $wpdb->posts WHERE ID = %d", $post_id ));
    $to_ping = trim($to_ping);
    $to_ping = preg_split('/\s/', $to_ping, -1, PREG_SPLIT_NO_EMPTY);
    $to_ping = apply_filters('get_to_ping',  $to_ping);
    return $to_ping;
}

/**
 * trackback_url_list() - Do trackbacks for a list of urls
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.0.0
 *
 * @param string $tb_list comma separated list of URLs
 * @param int $post_id post ID
 */
function trackback_url_list($tb_list, $post_id) {
    if (!empty($tb_list)) {
        // get post data
        $postdata = wp_get_single_post($post_id, ARRAY_A);

        // import postdata as variables
        extract($postdata, EXTR_SKIP);

        // form an excerpt
        $excerpt = strip_tags($post_excerpt?$post_excerpt:$post_content);

        if (strlen($excerpt) > 255) {
            $excerpt = substr($excerpt,0,252) . '...';
        }

        $trackback_urls = explode(',', $tb_list);
        foreach($trackback_urls as $tb_url) {
                $tb_url = trim($tb_url);
                trackback($tb_url, stripslashes($post_title), $excerpt, $post_id);
        }
        }
}

//
// Page functions
//

/**
 * get_all_page_ids() - Get a list of page IDs
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.0
 * @uses $wpdb
 *
 * @return array {@internal Missing Description}}
 */
function get_all_page_ids() {
    global $wpdb;

    if ( ! $page_ids = wp_cache_get('all_page_ids', 'posts') ) {
        $page_ids = $wpdb->get_col("SELECT ID FROM $wpdb->posts WHERE post_type = 'page'");
        wp_cache_add('all_page_ids', $page_ids, 'posts');
    }

    return $page_ids;
}

/**
 * get_page() - Retrieves page data given a page ID or page object
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5.1
 *
 * @param mixed &$page page object or page ID
 * @param string $output what to output
 * @param string $filter How the return value should be filtered.
 * @return mixed {@internal Missing Description}}
 */
function &get_page(&$page, $output = OBJECT, $filter = 'raw') {
    if ( empty($page) ) {
        if ( isset( $GLOBALS['page'] ) && isset( $GLOBALS['page']->ID ) )
            return get_post($GLOBALS['page'], $output, $filter);
        else
            return null;
    }

    return get_post($page, $output, $filter);
}

/**
 * get_page_by_path() - Retrieves a page given its path
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 * @uses $wpdb
 *
 * @param string $page_path page path
 * @param string $output output type
 * @return mixed {@internal Missing Description}}
 */
function get_page_by_path($page_path, $output = OBJECT) {
    global $wpdb;
    $page_path = rawurlencode(urldecode($page_path));
    $page_path = str_replace('%2F', '/', $page_path);
    $page_path = str_replace('%20', ' ', $page_path);
    $page_paths = '/' . trim($page_path, '/');
    $leaf_path  = sanitize_title(basename($page_paths));
    $page_paths = explode('/', $page_paths);
    foreach($page_paths as $pathdir)
        $full_path .= ($pathdir!=''?'/':'') . sanitize_title($pathdir);

    $pages = $wpdb->get_results( $wpdb->prepare( "SELECT ID, post_name, post_parent FROM $wpdb->posts WHERE post_name = %s AND (post_type = 'page' OR post_type = 'attachment')", $leaf_path ));

    if ( empty($pages) )
        return NULL;

    foreach ($pages as $page) {
        $path = '/' . $leaf_path;
        $curpage = $page;
        while ($curpage->post_parent != 0) {
            $curpage = $wpdb->get_row( $wpdb->prepare( "SELECT ID, post_name, post_parent FROM $wpdb->posts WHERE ID = %d and post_type='page'", $curpage->post_parent ));
            $path = '/' . $curpage->post_name . $path;
        }

        if ( $path == $full_path )
            return get_page($page->ID, $output);
    }

    return NULL;
}

/**
 * get_page_by_title() - Retrieve a page given its title
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 * @uses $wpdb
 *
 * @param string $page_title page title
 * @param string $output output type
 * @return mixed {@internal Missing Description}}
 */
function get_page_by_title($page_title, $output = OBJECT) {
    global $wpdb;
    $page = $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM $wpdb->posts WHERE post_title = %s AND post_type='page'", $page_title ));
    if ( $page )
        return get_page($page, $output);

    return NULL;
}

/**
 * get_page_children() - Retrieve child pages
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5.1
 *
 * @param int $page_id page ID
 * @param array $pages list of pages
 * @return array {@internal Missing Description}}
 */
function &get_page_children($page_id, $pages) {
    $page_list = array();
    foreach ( $pages as $page ) {
        if ( $page->post_parent == $page_id ) {
            $page_list[] = $page;
            if ( $children = get_page_children($page->ID, $pages) )
                $page_list = array_merge($page_list, $children);
        }
    }
    return $page_list;
}

/**
 * get_page_hierarchy() - {@internal Missing Short Description}}
 *
 * Fetches the pages returned as a FLAT list, but arranged in order of their hierarchy,
 * i.e., child parents immediately follow their parents.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.0
 *
 * @param array $posts posts array
 * @param int $parent parent page ID
 * @return array {@internal Missing Description}}
 */
function get_page_hierarchy($posts, $parent = 0) {
    $result = array ( );
    if ($posts) { foreach ($posts as $post) {
        if ($post->post_parent == $parent) {
            $result[$post->ID] = $post->post_name;
            $children = get_page_hierarchy($posts, $post->ID);
            $result += $children; //append $children to $result
        }
    } }
    return $result;
}

/**
 * get_page_uri() - Builds a page URI
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 *
 * @param int $page_id page ID
 * @return string {@internal Missing Description}}
 */
function get_page_uri($page_id) {
    $page = get_page($page_id);
    $uri = $page->post_name;

    // A page cannot be it's own parent.
    if ( $page->post_parent == $page->ID )
        return $uri;

    while ($page->post_parent != 0) {
        $page = get_page($page->post_parent);
        $uri = $page->post_name . "/" . $uri;
    }

    return $uri;
}

/**
 * get_pages() - Retrieve a list of pages
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.5
 * @uses $wpdb
 *
 * @param mixed $args Optional. Array or string of options
 * @return array List of pages matching defaults or $args
 */
function &get_pages($args = '') {
    global $wpdb;

    $defaults = array(
        'child_of' => 0, 'sort_order' => 'ASC',
        'sort_column' => 'post_title', 'hierarchical' => 1,
        'exclude' => '', 'include' => '',
        'meta_key' => '', 'meta_value' => '',
        'authors' => ''
    );

    $r = wp_parse_args( $args, $defaults );
    extract( $r, EXTR_SKIP );

    $key = md5( serialize( $r ) );
    if ( $cache = wp_cache_get( 'get_pages', 'posts' ) )
        if ( isset( $cache[ $key ] ) )
            return apply_filters('get_pages', $cache[ $key ], $r );

    $inclusions = '';
    if ( !empty($include) ) {
        $child_of = 0; //ignore child_of, exclude, meta_key, and meta_value params if using include
        $exclude = '';
        $meta_key = '';
        $meta_value = '';
        $hierarchical = false;
        $incpages = preg_split('/[\s,]+/',$include);
        if ( count($incpages) ) {
            foreach ( $incpages as $incpage ) {
                if (empty($inclusions))
                    $inclusions = $wpdb->prepare(' AND ( ID = %d ', $incpage);
                else
                    $inclusions .= $wpdb->prepare(' OR ID = %d ', $incpage);
            }
        }
    }
    if (!empty($inclusions))
        $inclusions .= ')';

    $exclusions = '';
    if ( !empty($exclude) ) {
        $expages = preg_split('/[\s,]+/',$exclude);
        if ( count($expages) ) {
            foreach ( $expages as $expage ) {
                if (empty($exclusions))
                    $exclusions = $wpdb->prepare(' AND ( ID <> %d ', $expage);
                else
                    $exclusions .= $wpdb->prepare(' AND ID <> %d ', $expage);
            }
        }
    }
    if (!empty($exclusions))
        $exclusions .= ')';

    $author_query = '';
    if (!empty($authors)) {
        $post_authors = preg_split('/[\s,]+/',$authors);

        if ( count($post_authors) ) {
            foreach ( $post_authors as $post_author ) {
                //Do we have an author id or an author login?
                if ( 0 == intval($post_author) ) {
                    $post_author = get_userdatabylogin($post_author);
                    if ( empty($post_author) )
                        continue;
                    if ( empty($post_author->ID) )
                        continue;
                    $post_author = $post_author->ID;
                }

                if ( '' == $author_query )
                    $author_query = $wpdb->prepare(' post_author = %d ', $post_author);
                else
                    $author_query .= $wpdb->prepare(' OR post_author = %d ', $post_author);
            }
            if ( '' != $author_query )
                $author_query = " AND ($author_query)";
        }
    }

    $join = '';
    $where = "$exclusions $inclusions ";
    if ( ! empty( $meta_key ) || ! empty( $meta_value ) ) {
        $join = " LEFT JOIN $wpdb->postmeta ON ( $wpdb->posts.ID = $wpdb->postmeta.post_id )";

        // meta_key and met_value might be slashed
        $meta_key = stripslashes($meta_key);
        $meta_value = stripslashes($meta_value);
        if ( ! empty( $meta_key ) )
            $where .= $wpdb->prepare(" AND $wpdb->postmeta.meta_key = %s", $meta_key);
        if ( ! empty( $meta_value ) )
            $where .= $wpdb->prepare(" AND $wpdb->postmeta.meta_value = %s", $meta_value);

    }
    $query = "SELECT * FROM $wpdb->posts $join WHERE (post_type = 'page' AND post_status = 'publish') $where ";
    $query .= $author_query;
    $query .= " ORDER BY " . $sort_column . " " . $sort_order ;

    $pages = $wpdb->get_results($query);

    if ( empty($pages) )
        return apply_filters('get_pages', array(), $r);

    // Update cache.
    update_page_cache($pages);

    if ( $child_of || $hierarchical )
        $pages = & get_page_children($child_of, $pages);

    $cache[ $key ] = $pages;
    wp_cache_set( 'get_pages', $cache, 'posts' );

    $pages = apply_filters('get_pages', $pages, $r);

    return $pages;
}

//
// Attachment functions
//

/**
 * is_local_attachment() - Check if the attachment URI is local one and is really an attachment.
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.0
 *
 * @param string $url URL to check
 * @return bool {@internal Missing Description}}
 */
function is_local_attachment($url) {
    if (strpos($url, get_bloginfo('url')) === false)
        return false;
    if (strpos($url, get_bloginfo('url') . '/?attachment_id=') !== false)
        return true;
    if ( $id = url_to_postid($url) ) {
        $post = & get_post($id);
        if ( 'attachment' == $post->post_type )
            return true;
    }
    return false;
}

/**
 * wp_insert_attachment() - Insert an attachment
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.0
 *
 * @uses $wpdb
 * @uses $user_ID
 *
 * @param object $object attachment object
 * @param string $file filename
 * @param int $post_parent parent post ID
 * @return int {@internal Missing Description}}
 */
function wp_insert_attachment($object, $file = false, $parent = 0) {
    global $wpdb, $user_ID;

    $defaults = array('post_status' => 'draft', 'post_type' => 'post', 'post_author' => $user_ID,
        'ping_status' => get_option('default_ping_status'), 'post_parent' => 0,
        'menu_order' => 0, 'to_ping' =>  '', 'pinged' => '', 'post_password' => '',
        'guid' => '', 'post_content_filtered' => '', 'post_excerpt' => '');

    $object = wp_parse_args($object, $defaults);
    if ( !empty($parent) )
        $object['post_parent'] = $parent;

    $object = sanitize_post($object, 'db');

    // export array as variables
    extract($object, EXTR_SKIP);

    // Make sure we set a valid category
    if (0 == count($post_category) || !is_array($post_category)) {
        $post_category = array(get_option('default_category'));
    }

    if ( empty($post_author) )
        $post_author = $user_ID;

    $post_type = 'attachment';
    $post_status = 'inherit';

    // Are we updating or creating?
    $update = false;
    if ( !empty($ID) ) {
        $update = true;
        $post_ID = (int) $ID;
    }

    // Create a valid post name.
    if ( empty($post_name) )
        $post_name = sanitize_title($post_title);
    else
        $post_name = sanitize_title($post_name);

    // expected_slashed ($post_name)
    $post_name_check = $wpdb->get_var( $wpdb->prepare( "SELECT post_name FROM $wpdb->posts WHERE post_name = '$post_name' AND post_status = 'inherit' AND ID != %d LIMIT 1", $post_ID));

    if ($post_name_check) {
        $suffix = 2;
        while ($post_name_check) {
            $alt_post_name = $post_name . "-$suffix";
            // expected_slashed ($alt_post_name, $post_name)
            $post_name_check = $wpdb->get_var( $wpdb->prepare( "SELECT post_name FROM $wpdb->posts WHERE post_name = '$alt_post_name' AND post_status = 'inherit' AND ID != %d AND post_parent = %d LIMIT 1", $post_ID, $post_parent));
            $suffix++;
        }
        $post_name = $alt_post_name;
    }

    if ( empty($post_date) )
        $post_date = current_time('mysql');
    if ( empty($post_date_gmt) )
        $post_date_gmt = current_time('mysql', 1);

    if ( empty($post_modified) )
                $post_modified = $post_date;
    if ( empty($post_modified_gmt) )
                $post_modified_gmt = $post_date_gmt;

    if ( empty($comment_status) ) {
        if ( $update )
            $comment_status = 'closed';
        else
            $comment_status = get_option('default_comment_status');
    }
    if ( empty($ping_status) )
        $ping_status = get_option('default_ping_status');

    if ( isset($to_ping) )
        $to_ping = preg_replace('|\s+|', "\n", $to_ping);
    else
        $to_ping = '';

    if ( isset($post_parent) )
        $post_parent = (int) $post_parent;
    else
        $post_parent = 0;

    if ( isset($menu_order) )
        $menu_order = (int) $menu_order;
    else
        $menu_order = 0;

    if ( !isset($post_password) )
        $post_password = '';

    if ( ! isset($pinged) )
        $pinged = '';

    // expected_slashed (everything!)
    $data = compact( array( 'post_author', 'post_date', 'post_date_gmt', 'post_content', 'post_content_filtered', 'post_title', 'post_excerpt', 'post_status', 'post_type', 'comment_status', 'ping_status', 'post_password', 'post_name', 'to_ping', 'pinged', 'post_modified', 'post_modified_gmt', 'post_parent', 'menu_order', 'post_mime_type', 'guid' ) );
    $data = stripslashes_deep( $data );

    if ( $update ) {
        $wpdb->update( $wpdb->posts, $data, array( 'ID' => $post_ID ) );
    } else {
        $wpdb->insert( $wpdb->posts, $data );
        $post_ID = (int) $wpdb->insert_id;
    }

    if ( empty($post_name) ) {
        $post_name = sanitize_title($post_title, $post_ID);
        $wpdb->update( $wpdb->posts, compact("post_name"), array( 'ID' => $post_ID ) );
    }

    wp_set_post_categories($post_ID, $post_category);

    if ( $file )
        update_attached_file( $post_ID, $file );

    clean_post_cache($post_ID);

    if ( $update) {
        do_action('edit_attachment', $post_ID);
    } else {
        do_action('add_attachment', $post_ID);
    }

    return $post_ID;
}

/**
 * wp_delete_attachment() - Delete an attachment
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.0
 * @uses $wpdb
 *
 * @param int $postid attachment Id
 * @return mixed {@internal Missing Description}}
 */
function wp_delete_attachment($postid) {
    global $wpdb;

    if ( !$post = $wpdb->get_row(  $wpdb->prepare( "SELECT * FROM $wpdb->posts WHERE ID = %d", $postid)) )
        return $post;

    if ( 'attachment' != $post->post_type )
        return false;

    $meta = wp_get_attachment_metadata( $postid );
    $file = get_attached_file( $postid );

    /** @todo Delete for pluggable post taxonomies too */
    wp_delete_object_term_relationships($postid, array('category', 'post_tag'));

    $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->posts WHERE ID = %d", $postid ));

    $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->comments WHERE comment_post_ID = %d", $postid ));

    $wpdb->query( $wpdb->prepare( "DELETE FROM $wpdb->postmeta WHERE post_id = %d ", $postid ));

    if ( ! empty($meta['thumb']) ) {
        // Don't delete the thumb if another attachment uses it
        if (! $wpdb->get_row( $wpdb->prepare( "SELECT meta_id FROM $wpdb->postmeta WHERE meta_key = '_wp_attachment_metadata' AND meta_value LIKE %s AND post_id <> %d", '%'.$meta['thumb'].'%', $postid)) ) {
            $thumbfile = str_replace(basename($file), $meta['thumb'], $file);
            $thumbfile = apply_filters('wp_delete_file', $thumbfile);
            @ unlink($thumbfile);
        }
    }

    // remove intermediate images if there are any
    $sizes = apply_filters('intermediate_image_sizes', array('thumbnail', 'medium'));
    foreach ( $sizes as $size ) {
        if ( $intermediate = image_get_intermediate_size($postid, $size) ) {
            $intermediate_file = apply_filters('wp_delete_file', $intermediate['path']);
            @ unlink($intermediate_file);
        }
    }

    $file = apply_filters('wp_delete_file', $file);

    if ( ! empty($file) )
        @ unlink($file);

    clean_post_cache($postid);

    do_action('delete_attachment', $postid);

    return $post;
}

/**
 * wp_get_attachment_metadata() - Retrieve metadata for an attachment
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @param int $post_id attachment ID
 * @param bool $unfiltered Optional, default is false. If true, filters are not run
 * @return array {@internal Missing Description}}
 */
function wp_get_attachment_metadata( $post_id, $unfiltered = false ) {
    $post_id = (int) $post_id;
    if ( !$post =& get_post( $post_id ) )
        return false;

    $data = get_post_meta( $post->ID, '_wp_attachment_metadata', true );
    if ( $unfiltered )
        return $data;
    return apply_filters( 'wp_get_attachment_metadata', $data, $post->ID );
}

/**
 * wp_update_attachment_metadata() - Update metadata for an attachment
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @param int $post_id attachment ID
 * @param array $data attachment data
 * @return int {@internal Missing Description}}
 */
function wp_update_attachment_metadata( $post_id, $data ) {
    $post_id = (int) $post_id;
    if ( !$post =& get_post( $post_id ) )
        return false;

    $data = apply_filters( 'wp_update_attachment_metadata', $data, $post->ID );

    return update_post_meta( $post->ID, '_wp_attachment_metadata', $data);
}

/**
 * wp_get_attachment_url() - Retrieve the URL for an attachment
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @param int $post_id attachment ID
 * @return string {@internal Missing Description}}
 */
function wp_get_attachment_url( $post_id = 0 ) {
    $post_id = (int) $post_id;
    if ( !$post =& get_post( $post_id ) )
        return false;

    $url = get_the_guid( $post->ID );

    if ( 'attachment' != $post->post_type || !$url )
        return false;

    return apply_filters( 'wp_get_attachment_url', $url, $post->ID );
}

/**
 * wp_get_attachment_thumb_file() - Retrieve thumbnail for an attachment
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @param int $post_id attachment ID
 * @return mixed {@internal Missing Description}}
 */
function wp_get_attachment_thumb_file( $post_id = 0 ) {
    $post_id = (int) $post_id;
    if ( !$post =& get_post( $post_id ) )
        return false;
    if ( !is_array( $imagedata = wp_get_attachment_metadata( $post->ID ) ) )
        return false;

    $file = get_attached_file( $post->ID );

    if ( !empty($imagedata['thumb']) && ($thumbfile = str_replace(basename($file), $imagedata['thumb'], $file)) && file_exists($thumbfile) )
        return apply_filters( 'wp_get_attachment_thumb_file', $thumbfile, $post->ID );
    return false;
}

/**
 * wp_get_attachment_thumb_url() - Retrieve URL for an attachment thumbnail
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @param int $post_id attachment ID
 * @return string {@internal Missing Description}}
 */
function wp_get_attachment_thumb_url( $post_id = 0 ) {
    $post_id = (int) $post_id;
    if ( !$post =& get_post( $post_id ) )
        return false;
    if ( !$url = wp_get_attachment_url( $post->ID ) )
        return false;

    $sized = image_downsize( $post_id, 'thumbnail' );
    if ( $sized )
        return $sized[0];

    if ( !$thumb = wp_get_attachment_thumb_file( $post->ID ) )
        return false;

    $url = str_replace(basename($url), basename($thumb), $url);

    return apply_filters( 'wp_get_attachment_thumb_url', $url, $post->ID );
}

/**
 * wp_attachment_is_image() - Check if the attachment is an image
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @param int $post_id attachment ID
 * @return bool {@internal Missing Description}}
 */
function wp_attachment_is_image( $post_id = 0 ) {
    $post_id = (int) $post_id;
    if ( !$post =& get_post( $post_id ) )
        return false;

    if ( !$file = get_attached_file( $post->ID ) )
        return false;

    $ext = preg_match('/\.([^.]+)$/', $file, $matches) ? strtolower($matches[1]) : false;

    $image_exts = array('jpg', 'jpeg', 'gif', 'png');

    if ( 'image/' == substr($post->post_mime_type, 0, 6) || $ext && 'import' == $post->post_mime_type && in_array($ext, $image_exts) )
        return true;
    return false;
}

/**
 * wp_mime_type_icon() - Retrieve the icon for a MIME type
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @param string $mime MIME type
 * @return string|bool {@internal Missing Description}}
 */
function wp_mime_type_icon( $mime = 0 ) {
    if ( !is_numeric($mime) )
        $icon = wp_cache_get("mime_type_icon_$mime");
    if ( empty($icon) ) {
        $post_id = 0;
        $post_mimes = array();
        if ( is_numeric($mime) ) {
            $mime = (int) $mime;
            if ( $post =& get_post( $mime ) ) {
                $post_id = (int) $post->ID;
                $ext = preg_replace('/^.+?\.([^.]+)$/', '$1', $post->guid);
                if ( !empty($ext) ) {
                    $post_mimes[] = $ext;
                    if ( $ext_type = wp_ext2type( $ext ) )
                        $post_mimes[] = $ext_type;
                }
                $mime = $post->post_mime_type;
            } else {
                $mime = 0;
            }
        } else {
            $post_mimes[] = $mime;
        }

        $icon_files = wp_cache_get('icon_files');

        if ( !is_array($icon_files) ) {
            $icon_dir = apply_filters( 'icon_dir', ABSPATH . WPINC . '/images/crystal' );
            $icon_dir_uri = apply_filters( 'icon_dir_uri', includes_url('images/crystal') );
            $dirs = apply_filters( 'icon_dirs', array($icon_dir => $icon_dir_uri) );
            $icon_files = array();
            while ( $dirs ) {
                $dir = array_shift($keys = array_keys($dirs));
                $uri = array_shift($dirs);
                if ( $dh = opendir($dir) ) {
                    while ( false !== $file = readdir($dh) ) {
                        $file = basename($file);
                        if ( substr($file, 0, 1) == '.' )
                            continue;
                        if ( !in_array(strtolower(substr($file, -4)), array('.png', '.gif', '.jpg') ) ) {
                            if ( is_dir("$dir/$file") )
                                $dirs["$dir/$file"] = "$uri/$file";
                            continue;
                        }
                        $icon_files["$dir/$file"] = "$uri/$file";
                    }
                    closedir($dh);
                }
            }
            wp_cache_set('icon_files', $icon_files, 600);
        }

        // Icon basename - extension = MIME wildcard
        foreach ( $icon_files as $file => $uri )
            $types[ preg_replace('/^([^.]*).*$/', '$1', basename($file)) ] =& $icon_files[$file];

        if ( ! empty($mime) ) {
            $post_mimes[] = substr($mime, 0, strpos($mime, '/'));
            $post_mimes[] = substr($mime, strpos($mime, '/') + 1);
            $post_mimes[] = str_replace('/', '_', $mime);
        }

        $matches = wp_match_mime_types(array_keys($types), $post_mimes);
        $matches['default'] = array('default');

        foreach ( $matches as $match => $wilds ) {
            if ( isset($types[$wilds[0]])) {
                $icon = $types[$wilds[0]];
                if ( !is_numeric($mime) )
                    wp_cache_set("mime_type_icon_$mime", $icon);
                break;
            }
        }
    }

    return apply_filters( 'wp_mime_type_icon', $icon, $mime, $post_id ); // Last arg is 0 if function pass mime type.
}

/**
 * wp_check_for_changed_slugs() - {@internal Missing Short Description}}
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.1
 *
 * @param int $post_id The Post ID
 * @return int Same as $post_id
 */
function wp_check_for_changed_slugs($post_id) {
    if ( !isset($_POST['wp-old-slug']) || !strlen($_POST['wp-old-slug']) )
        return $post_id;

    $post = &get_post($post_id);

    // we're only concerned with published posts
    if ( $post->post_status != 'publish' || $post->post_type != 'post' )
        return $post_id;

    // only bother if the slug has changed
    if ( $post->post_name == $_POST['wp-old-slug'] )
        return $post_id;

    $old_slugs = (array) get_post_meta($post_id, '_wp_old_slug');

    // if we haven't added this old slug before, add it now
    if ( !count($old_slugs) || !in_array($_POST['wp-old-slug'], $old_slugs) )
        add_post_meta($post_id, '_wp_old_slug', $_POST['wp-old-slug']);

    // if the new slug was used previously, delete it from the list
    if ( in_array($post->post_name, $old_slugs) )
        delete_post_meta($post_id, '_wp_old_slug', $post->post_name);

    return $post_id;
}

/**
 * get_private_posts_cap_sql() - {@internal Missing Short Description}}
 *
 * This function provides a standardized way to appropriately select on
 * the post_status of posts/pages. The function will return a piece of
 * SQL code that can be added to a WHERE clause; this SQL is constructed
 * to allow all published posts, and all private posts to which the user
 * has access.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.2
 *
 * @uses $user_ID
 * @uses apply_filters() Call 'pub_priv_sql_capability' filter for plugins with different post types
 *
 * @param string $post_type currently only supports 'post' or 'page'.
 * @return string SQL code that can be added to a where clause.
 */
function get_private_posts_cap_sql($post_type) {
    global $user_ID;
    $cap = '';

    // Private posts
    if ($post_type == 'post') {
        $cap = 'read_private_posts';
    // Private pages
    } elseif ($post_type == 'page') {
        $cap = 'read_private_pages';
    // Dunno what it is, maybe plugins have their own post type?
    } else {
        $cap = apply_filters('pub_priv_sql_capability', $cap);

        if (empty($cap)) {
            // We don't know what it is, filters don't change anything,
            // so set the SQL up to return nothing.
            return '1 = 0';
        }
    }

    $sql = '(post_status = \'publish\'';

    if (current_user_can($cap)) {
        // Does the user have the capability to view private posts? Guess so.
        $sql .= ' OR post_status = \'private\'';
    } elseif (is_user_logged_in()) {
        // Users can view their own private posts.
        $sql .= ' OR post_status = \'private\' AND post_author = \'' . $user_ID . '\'';
    }

    $sql .= ')';

    return $sql;
}

/**
 * get_lastpostdate() - {@internal Missing Short Description}}
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 0.71
 *
 * @uses $wpdb
 * @uses $blog_id
 * @uses apply_filters() Calls 'get_lastpostdate' filter
 *
 * @global mixed $cache_lastpostdate Stores the last post date
 * @global mixed $pagenow The current page being viewed
 *
 * @param string $timezone The location to get the time. Can be 'gmt', 'blog', or 'server'.
 * @return string The date of the last post.
 */
function get_lastpostdate($timezone = 'server') {
    global $cache_lastpostdate, $wpdb, $blog_id;
    $add_seconds_server = date('Z');
    if ( !isset($cache_lastpostdate[$blog_id][$timezone]) ) {
        switch(strtolower($timezone)) {
            case 'gmt':
                $lastpostdate = $wpdb->get_var("SELECT post_date_gmt FROM $wpdb->posts WHERE post_status = 'publish' ORDER BY post_date_gmt DESC LIMIT 1");
                break;
            case 'blog':
                $lastpostdate = $wpdb->get_var("SELECT post_date FROM $wpdb->posts WHERE post_status = 'publish' ORDER BY post_date_gmt DESC LIMIT 1");
                break;
            case 'server':
                $lastpostdate = $wpdb->get_var("SELECT DATE_ADD(post_date_gmt, INTERVAL '$add_seconds_server' SECOND) FROM $wpdb->posts WHERE post_status = 'publish' ORDER BY post_date_gmt DESC LIMIT 1");
                break;
        }
        $cache_lastpostdate[$blog_id][$timezone] = $lastpostdate;
    } else {
        $lastpostdate = $cache_lastpostdate[$blog_id][$timezone];
    }
    return apply_filters( 'get_lastpostdate', $lastpostdate, $timezone );
}

/**
 * get_lastpostmodified() - {@internal Missing Short Description}}
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 1.2
 *
 * @uses $wpdb
 * @uses $blog_id
 * @uses apply_filters() Calls 'get_lastpostmodified' filter
 *
 * @global mixed $cache_lastpostmodified Stores the date the last post was modified
 * @global mixed $pagenow The current page being viewed
 *
 * @param string $timezone The location to get the time. Can be 'gmt', 'blog', or 'server'.
 * @return string The date the post was last modified.
 */
function get_lastpostmodified($timezone = 'server') {
    global $cache_lastpostmodified, $wpdb, $blog_id;
    $add_seconds_server = date('Z');
    if ( !isset($cache_lastpostmodified[$blog_id][$timezone]) ) {
        switch(strtolower($timezone)) {
            case 'gmt':
                $lastpostmodified = $wpdb->get_var("SELECT post_modified_gmt FROM $wpdb->posts WHERE post_status = 'publish' ORDER BY post_modified_gmt DESC LIMIT 1");
                break;
            case 'blog':
                $lastpostmodified = $wpdb->get_var("SELECT post_modified FROM $wpdb->posts WHERE post_status = 'publish' ORDER BY post_modified_gmt DESC LIMIT 1");
                break;
            case 'server':
                $lastpostmodified = $wpdb->get_var("SELECT DATE_ADD(post_modified_gmt, INTERVAL '$add_seconds_server' SECOND) FROM $wpdb->posts WHERE post_status = 'publish' ORDER BY post_modified_gmt DESC LIMIT 1");
                break;
        }
        $lastpostdate = get_lastpostdate($timezone);
        if ( $lastpostdate > $lastpostmodified ) {
            $lastpostmodified = $lastpostdate;
        }
        $cache_lastpostmodified[$blog_id][$timezone] = $lastpostmodified;
    } else {
        $lastpostmodified = $cache_lastpostmodified[$blog_id][$timezone];
    }
    return apply_filters( 'get_lastpostmodified', $lastpostmodified, $timezone );
}

/**
 * update_post_cache() - Updates posts in cache
 *
 * @usedby update_page_cache() update_page_cache() aliased by this function.
 *
 * @package WordPress
 * @subpackage Cache
 * @since 1.5.1
 *
 * @param array $posts Array of post objects
 */
function update_post_cache(&$posts) {
    if ( !$posts )
        return;

    foreach ( $posts as $post )
        wp_cache_add($post->ID, $post, 'posts');
}

/**
 * clean_post_cache() - Will clean the post in the cache
 *
 * Cleaning means delete from the cache of the post. Will call to clean
 * the term object cache associated with the post ID.
 *
 * @package WordPress
 * @subpackage Cache
 * @since 2.0
 *
 * @uses do_action() Will call the 'clean_post_cache' hook action.
 *
 * @param int $id The Post ID in the cache to clean
 */
function clean_post_cache($id) {
    global $wpdb;
    $id = (int) $id;

    wp_cache_delete($id, 'posts');
    wp_cache_delete($id, 'post_meta');

    clean_object_term_cache($id, 'post');

    wp_cache_delete( 'wp_get_archives', 'general' );

    do_action('clean_post_cache', $id);

    if ( $children = $wpdb->get_col( $wpdb->prepare("SELECT ID FROM $wpdb->posts WHERE post_parent = %d", $id) ) ) {
        foreach( $children as $cid )
            clean_post_cache( $cid );
    }
}

/**
 * update_page_cache() - Alias of update_post_cache()
 *
 * @see update_post_cache() Posts and pages are the same, alias is intentional
 *
 * @package WordPress
 * @subpackage Cache
 * @since 1.5.1
 *
 * @param array $pages list of page objects
 */
function update_page_cache(&$pages) {
    update_post_cache($pages);
}

/**
 * clean_page_cache() - Will clean the page in the cache
 *
 * Clean (read: delete) page from cache that matches $id. Will also clean
 * cache associated with 'all_page_ids' and 'get_pages'.
 *
 * @package WordPress
 * @subpackage Cache
 * @since 2.0
 *
 * @uses do_action() Will call the 'clean_page_cache' hook action.
 *
 * @param int $id Page ID to clean
 */
function clean_page_cache($id) {
    clean_post_cache($id);

    wp_cache_delete( 'all_page_ids', 'posts' );
    wp_cache_delete( 'get_pages', 'posts' );

    do_action('clean_page_cache', $id);
}

/**
 * update_post_caches() - Call major cache updating functions for list of Post objects.
 *
 * @package WordPress
 * @subpackage Cache
 * @since 1.5
 *
 * @uses $wpdb
 * @uses update_post_cache()
 * @uses update_object_term_cache()
 * @uses update_postmeta_cache()
 *
 * @param array $posts Array of Post objects
 */
function update_post_caches(&$posts) {
    // No point in doing all this work if we didn't match any posts.
    if ( !$posts )
        return;

    update_post_cache($posts);

    $post_ids = array();

    for ($i = 0; $i < count($posts); $i++)
        $post_ids[] = $posts[$i]->ID;

    update_object_term_cache($post_ids, 'post');

    update_postmeta_cache($post_ids);
}

/**
 * update_postmeta_cache() - {@internal Missing Short Description}}
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Cache
 * @since 2.1
 *
 * @uses $wpdb
 *
 * @param array $post_ids {@internal Missing Description}}
 * @return bool|array Returns false if there is nothing to update or an array of metadata
 */
function update_postmeta_cache($post_ids) {
    global $wpdb;

    if ( empty( $post_ids ) )
        return false;

    if ( !is_array($post_ids) ) {
        $post_ids = preg_replace('|[^0-9,]|', '', $post_ids);
        $post_ids = explode(',', $post_ids);
    }

    $post_ids = array_map('intval', $post_ids);

    $ids = array();
    foreach ( (array) $post_ids as $id ) {
        if ( false === wp_cache_get($id, 'post_meta') )
            $ids[] = $id;
    }

    if ( empty( $ids ) )
        return false;

    // Get post-meta info
    $id_list = join(',', $ids);
    $cache = array();
    if ( $meta_list = $wpdb->get_results("SELECT post_id, meta_key, meta_value FROM $wpdb->postmeta WHERE post_id IN ($id_list) ORDER BY post_id, meta_key", ARRAY_A) ) {
        foreach ( (array) $meta_list as $metarow) {
            $mpid = (int) $metarow['post_id'];
            $mkey = $metarow['meta_key'];
            $mval = $metarow['meta_value'];

            // Force subkeys to be array type:
            if ( !isset($cache[$mpid]) || !is_array($cache[$mpid]) )
                $cache[$mpid] = array();
            if ( !isset($cache[$mpid][$mkey]) || !is_array($cache[$mpid][$mkey]) )
                $cache[$mpid][$mkey] = array();

            // Add a value to the current pid/key:
            $cache[$mpid][$mkey][] = $mval;
        }
    }

    foreach ( (array) $ids as $id ) {
        if ( ! isset($cache[$id]) )
            $cache[$id] = array();
    }

    foreach ( array_keys($cache) as $post)
        wp_cache_set($post, $cache[$post], 'post_meta');

    return $cache;
}

//
// Hooks
//

/**
 * _transition_post_status() - Hook {@internal Missing Short Description}}
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 *
 * @uses $wpdb
 *
 * @param string $new_status {@internal Missing Description}}
 * @param string $old_status {@internal Missing Description}}
 * @param object $post Object type containing the post information
 */
function _transition_post_status($new_status, $old_status, $post) {
    global $wpdb;

    if ( $old_status != 'publish' && $new_status == 'publish' ) {
        // Reset GUID if transitioning to publish and it is empty
        if ( '' == get_the_guid($post->ID) )
            $wpdb->update( $wpdb->posts, array( 'guid' => get_permalink( $post->ID ) ), array( 'ID' => $post->ID ) );
        do_action('private_to_published', $post->ID);  // Deprecated, use private_to_publish
    }

    // Always clears the hook in case the post status bounced from future to draft.
    wp_clear_scheduled_hook('publish_future_post', $post->ID);
}

/**
 * _future_post_hook() - Hook used to schedule publication for a post marked for the future.
 *
 * The $post properties used and must exist are 'ID' and 'post_date_gmt'.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 *
 * @param int $post_id Not Used. Can be set to null.
 * @param object $post Object type containing the post information
 */
function _future_post_hook($deprecated = '', $post) {
    wp_clear_scheduled_hook( 'publish_future_post', $post->ID );
    wp_schedule_single_event(strtotime($post->post_date_gmt. ' GMT'), 'publish_future_post', array($post->ID));
}

/**
 * _publish_post_hook() - Hook {@internal Missing Short Description}}
 *
 * {@internal Missing Long Description}}
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 *
 * @uses $wpdb
 * @uses XMLRPC_REQUEST
 * @uses APP_REQUEST
 * @uses do_action Calls 'xmlprc_publish_post' action if XMLRPC_REQUEST is defined. Calls 'app_publish_post'
 *    action if APP_REQUEST is defined.
 *
 * @param int $post_id The ID in the database table of the post being published
 */
function _publish_post_hook($post_id) {
    global $wpdb;

    if ( defined('XMLRPC_REQUEST') )
        do_action('xmlrpc_publish_post', $post_id);
    if ( defined('APP_REQUEST') )
        do_action('app_publish_post', $post_id);

    if ( defined('WP_IMPORTING') )
        return;

    $data = array( 'post_id' => $post_id, 'meta_value' => '1' );
    if ( get_option('default_pingback_flag') )
        $wpdb->insert( $wpdb->postmeta, $data + array( 'meta_key' => '_pingme' ) );
    $wpdb->insert( $wpdb->postmeta, $data + array( 'meta_key' => '_encloseme' ) );
    wp_schedule_single_event(time(), 'do_pings');
}

/**
 * _save_post_hook() - Hook used to prevent page/post cache and rewrite rules from staying dirty
 *
 * Does two things. If the post is a page and has a template then it will update/add that
 * template to the meta. For both pages and posts, it will clean the post cache to make sure
 * that the cache updates to the changes done recently. For pages, the rewrite rules of
 * WordPress are flushed to allow for any changes.
 *
 * The $post parameter, only uses 'post_type' property and 'page_template' property.
 *
 * @package WordPress
 * @subpackage Post
 * @since 2.3
 *
 * @uses $wp_rewrite Flushes Rewrite Rules.
 *
 * @param int $post_id The ID in the database table for the $post
 * @param object $post Object type containing the post information
 */
function _save_post_hook($post_id, $post) {
    if ( $post->post_type == 'page' ) {
        clean_page_cache($post_id);
        global $wp_rewrite;
        $wp_rewrite->flush_rules();
    } else {
        clean_post_cache($post_id);
    }
}

//
// Private
//

function _get_post_ancestors(&$_post) {
    global $wpdb;

    if ( isset($_post->ancestors) )
        return;

    $_post->ancestors = array();

    if ( empty($_post->post_parent) || $_post->ID == $_post->post_parent )
        return;

    $id = $_post->ancestors[] = $_post->post_parent;
    while ( $ancestor = $wpdb->get_var( $wpdb->prepare("SELECT `post_parent` FROM $wpdb->posts WHERE ID = %d LIMIT 1", $id) ) ) {
        if ( $id == $ancestor )
            break;
        $id = $_post->ancestors[] = $ancestor;
    }
}

/* Post Revisions */

/**
 * _wp_post_revision_fields() - determines which fields of posts are to be saved in revisions
 *
 * Does two things. If passed a post *array*, it will return a post array ready to be
 * insterted into the posts table as a post revision.
 * Otherwise, returns an array whose keys are the post fields to be saved for post revisions.
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @param array $post optional a post array to be processed for insertion as a post revision
 * @param bool $autosave optional Is the revision an autosave?
 * @return array post array ready to be inserted as a post revision or array of fields that can be versioned
 */
function _wp_post_revision_fields( $post = null, $autosave = false ) {
    static $fields = false;

    if ( !$fields ) {
        // Allow these to be versioned
        $fields = array(
            'post_title' => __( 'Title' ),
            'post_content' => __( 'Content' ),
            'post_excerpt' => __( 'Excerpt' ),
        );

        // Runs only once
        $fields = apply_filters( '_wp_post_revision_fields', $fields );

        // WP uses these internally either in versioning or elsewhere - they cannot be versioned
        foreach ( array( 'ID', 'post_name', 'post_parent', 'post_date', 'post_date_gmt', 'post_status', 'post_type', 'comment_count', 'post_author' ) as $protect )
            unset( $fields[$protect] );
    }

    if ( !is_array($post) )
        return $fields;

    $return = array();
    foreach ( array_intersect( array_keys( $post ), array_keys( $fields ) ) as $field )
        $return[$field] = $post[$field];

    $return['post_parent']   = $post['ID'];
    $return['post_status']   = 'inherit';
    $return['post_type']     = 'revision';
    $return['post_name']     = $autosave ? "$post[ID]-autosave" : "$post[ID]-revision";
    $return['post_date']     = $post['post_modified'];
    $return['post_date_gmt'] = $post['post_modified_gmt'];

    return $return;
}

/**
 * wp_save_post_revision() - Saves an already existing post as a post revision.  Typically used immediately prior to post updates.
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @uses _wp_put_post_revision()
 *
 * @param int $post_id The ID of the post to save as a revision
 * @return mixed null or 0 if error, new revision ID if success
 */
function wp_save_post_revision( $post_id ) {
    // We do autosaves manually with wp_create_post_autosave()
    if ( @constant( 'DOING_AUTOSAVE' ) )
        return;

    // WP_POST_REVISIONS = 0, false
    if ( !constant('WP_POST_REVISIONS') )
        return;

    if ( !$post = get_post( $post_id, ARRAY_A ) )
        return;

    if ( !in_array( $post['post_type'], array( 'post', 'page' ) ) )
        return;

    $return = _wp_put_post_revision( $post );

    // WP_POST_REVISIONS = true (default), -1
    if ( !is_numeric( WP_POST_REVISIONS ) || WP_POST_REVISIONS < 0 )
        return $return;

    // all revisions and (possibly) one autosave
    $revisions = wp_get_post_revisions( $post_id, array( 'order' => 'ASC' ) );

    // WP_POST_REVISIONS = (int) (# of autasaves to save)
    $delete = count($revisions) - WP_POST_REVISIONS;

    if ( $delete < 1 )
        return $return;

    $revisions = array_slice( $revisions, 0, $delete );

    for ( $i = 0; isset($revisions[$i]); $i++ ) {
        if ( false !== strpos( $revisions[$i]->post_name, 'autosave' ) )
            continue;
        wp_delete_post_revision( $revisions[$i]->ID );
    }

    return $return;
}

/**
 * wp_get_post_autosave() - returns the autosaved data of the specified post.
 *
 * Returns a post object containing the information that was autosaved for the specified post.
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @param int $post_id The post ID
 * @return object|bool the autosaved data or false on failure or when no autosave exists
 */
function wp_get_post_autosave( $post_id ) {
    global $wpdb;
    if ( !$post = get_post( $post_id ) )
        return false;

    $q = array(
        'name' => "{$post->ID}-autosave",
        'post_parent' => $post->ID,
        'post_type' => 'revision',
        'post_status' => 'inherit'
    );

    // Use WP_Query so that the result gets cached
    $autosave_query = new WP_Query;

    add_action( 'parse_query', '_wp_get_post_autosave_hack' );
    $autosave = $autosave_query->query( $q );
    remove_action( 'parse_query', '_wp_get_post_autosave_hack' );

    if ( $autosave && is_array($autosave) && is_object($autosave[0]) )
        return $autosave[0];

    return false;
}

// Internally used to hack WP_Query into submission
function _wp_get_post_autosave_hack( $query ) {
    $query->is_single = false;
}


/**
 * wp_is_post_revision() - Determines if the specified post is a revision.
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @param int|object $post post ID or post object
 * @return bool|int false if not a revision, ID of revision's parent otherwise
 */
function wp_is_post_revision( $post ) {
    if ( !$post = wp_get_post_revision( $post ) )
        return false;
    return (int) $post->post_parent;
}

/**
 * wp_is_post_autosave() - Determines if the specified post is an autosave.
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @param int|object $post post ID or post object
 * @return bool|int false if not a revision, ID of autosave's parent otherwise
 */
function wp_is_post_autosave( $post ) {
    if ( !$post = wp_get_post_revision( $post ) )
        return false;
    if ( "{$post->post_parent}-autosave" !== $post->post_name )
        return false;
    return (int) $post->post_parent;
}

/**
 * _wp_put_post_revision() - Inserts post data into the posts table as a post revision
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @uses wp_insert_post()
 *
 * @param int|object|array $post post ID, post object OR post array
 * @param bool $autosave optional Is the revision an autosave?
 * @return mixed null or 0 if error, new revision ID if success
 */
function _wp_put_post_revision( $post = null, $autosave = false ) {
    if ( is_object($post) )
        $post = get_object_vars( $post );
    elseif ( !is_array($post) )
        $post = get_post($post, ARRAY_A);
    if ( !$post || empty($post['ID']) )
        return;

    if ( isset($post['post_type']) && 'revision' == $post_post['type'] )
        return new WP_Error( 'post_type', __( 'Cannot create a revision of a revision' ) );

    $post = _wp_post_revision_fields( $post, $autosave );

    $revision_id = wp_insert_post( $post );
    if ( is_wp_error($revision_id) )
        return $revision_id;

    if ( $revision_id )
        do_action( '_wp_put_post_revision', $revision_id );
    return $revision_id;
}

/**
 * wp_get_post_revision() - Gets a post revision
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @uses get_post()
 *
 * @param int|object $post post ID or post object
 * @param $output optional OBJECT, ARRAY_A, or ARRAY_N
 * @param string $filter optional sanitation filter.  @see sanitize_post()
 * @return mixed null if error or post object if success
 */
function &wp_get_post_revision(&$post, $output = OBJECT, $filter = 'raw') {
    $null = null;
    if ( !$revision = get_post( $post, OBJECT, $filter ) )
        return $revision;
    if ( 'revision' !== $revision->post_type )
        return $null;

    if ( $output == OBJECT ) {
        return $revision;
    } elseif ( $output == ARRAY_A ) {
        $_revision = get_object_vars($revision);
        return $_revision;
    } elseif ( $output == ARRAY_N ) {
        $_revision = array_values(get_object_vars($revision));
        return $_revision;
    }

    return $revision;
}

/**
 * wp_restore_post_revision() - Restores a post to the specified revision
 *
 * Can restore a past using all fields of the post revision, or only selected fields.
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @uses wp_get_post_revision()
 * @uses wp_update_post()
 *
 * @param int|object $revision_id revision ID or revision object
 * @param array $fields optional What fields to restore from.  Defaults to all.
 * @return mixed null if error, false if no fields to restore, (int) post ID if success
 */
function wp_restore_post_revision( $revision_id, $fields = null ) {
    if ( !$revision = wp_get_post_revision( $revision_id, ARRAY_A ) )
        return $revision;

    if ( !is_array( $fields ) )
        $fields = array_keys( _wp_post_revision_fields() );

    $update = array();
    foreach( array_intersect( array_keys( $revision ), $fields ) as $field )
        $update[$field] = $revision[$field];

    if ( !$update )
        return false;

    $update['ID'] = $revision['post_parent'];

    $post_id = wp_update_post( $update );
    if ( is_wp_error( $post_id ) )
        return $post_id;

    if ( $post_id )
        do_action( 'wp_restore_post_revision', $post_id, $revision['ID'] );

    return $post_id;
}

/**
 * wp_delete_post_revision() - Deletes a revision.
 *
 * Deletes the row from the posts table corresponding to the specified revision
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @uses wp_get_post_revision()
 * @uses wp_delete_post()
 *
 * @param int|object $revision_id revision ID or revision object
 * @param array $fields optional What fields to restore from.  Defaults to all.
 * @return mixed null if error, false if no fields to restore, (int) post ID if success
 */
function wp_delete_post_revision( $revision_id ) {
    if ( !$revision = wp_get_post_revision( $revision_id ) )
        return $revision;

    $delete = wp_delete_post( $revision->ID );
    if ( is_wp_error( $delete ) )
        return $delete;

    if ( $delete )
        do_action( 'wp_delete_post_revision', $revision->ID, $revision );

    return $delete;
}

/**
 * wp_get_post_revisions() - Returns all revisions of specified post
 *
 * @package WordPress
 * @subpackage Post Revisions
 * @since 2.6
 *
 * @uses get_children()
 *
 * @param int|object $post_id post ID or post object
 * @return array empty if no revisions
 */
function wp_get_post_revisions( $post_id = 0, $args = null ) {
    if ( !constant('WP_POST_REVISIONS') )
        return array();
    if ( ( !$post = get_post( $post_id ) ) || empty( $post->ID ) )
        return array();

    $defaults = array( 'order' => 'DESC', 'orderby' => 'date' );
    $args = wp_parse_args( $args, $defaults );
    $args = array_merge( $args, array( 'post_parent' => $post->ID, 'post_type' => 'revision', 'post_status' => 'inherit' ) );

    if ( !$revisions = get_children( $args ) )
        return array();
    return $revisions;
}