HTML Examples/WP.iso/wordpress/wp-includes/post-template.php

PHP Script | 2017-09-24 | 57.3 KB | 1,827 lines

<?php
/**
 * WordPress Post Template Functions.
 *
 * Gets content for the current post in the loop.
 *
 * @package WordPress
 * @subpackage Template
 */

/**
 * Display the ID of the current item in the WordPress Loop.
 *
 * @since 0.71
 */
function the_ID() {
    echo get_the_ID();
}

/**
 * Retrieve the ID of the current item in the WordPress Loop.
 *
 * @since 2.1.0
 *
 * @return int|false The ID of the current item in the WordPress Loop. False if $post is not set.
 */
function get_the_ID() {
    $post = get_post();
    return ! empty( $post ) ? $post->ID : false;
}

/**
 * Display or retrieve the current post title with optional markup.
 *
 * @since 0.71
 *
 * @param string $before Optional. Markup to prepend to the title. Default empty.
 * @param string $after  Optional. Markup to append to the title. Default empty.
 * @param bool   $echo   Optional. Whether to echo or return the title. Default true for echo.
 * @return string|void Current post title if $echo is false.
 */
function the_title( $before = '', $after = '', $echo = true ) {
    $title = get_the_title();

    if ( strlen($title) == 0 )
        return;

    $title = $before . $title . $after;

    if ( $echo )
        echo $title;
    else
        return $title;
}

/**
 * Sanitize the current title when retrieving or displaying.
 *
 * Works like the_title(), except the parameters can be in a string or
 * an array. See the function for what can be override in the $args parameter.
 *
 * The title before it is displayed will have the tags stripped and esc_attr()
 * before it is passed to the user or displayed. The default as with the_title(),
 * is to display the title.
 *
 * @since 2.3.0
 *
 * @param string|array $args {
 *     Title attribute arguments. Optional.
 *
 *     @type string  $before Markup to prepend to the title. Default empty.
 *     @type string  $after  Markup to append to the title. Default empty.
 *     @type bool    $echo   Whether to echo or return the title. Default true for echo.
 *     @type WP_Post $post   Current post object to retrieve the title for.
 * }
 * @return string|void String when echo is false.
 */
function the_title_attribute( $args = '' ) {
    $defaults = array( 'before' => '', 'after' =>  '', 'echo' => true, 'post' => get_post() );
    $r = wp_parse_args( $args, $defaults );

    $title = get_the_title( $r['post'] );

    if ( strlen( $title ) == 0 ) {
        return;
    }

    $title = $r['before'] . $title . $r['after'];
    $title = esc_attr( strip_tags( $title ) );

    if ( $r['echo'] ) {
        echo $title;
    } else {
        return $title;
    }
}

/**
 * Retrieve post title.
 *
 * If the post is protected and the visitor is not an admin, then "Protected"
 * will be displayed before the post title. If the post is private, then
 * "Private" will be located before the post title.
 *
 * @since 0.71
 *
 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
 * @return string
 */
function get_the_title( $post = 0 ) {
    $post = get_post( $post );

    $title = isset( $post->post_title ) ? $post->post_title : '';
    $id = isset( $post->ID ) ? $post->ID : 0;

    if ( ! is_admin() ) {
        if ( ! empty( $post->post_password ) ) {

            /**
             * Filters the text prepended to the post title for protected posts.
             *
             * The filter is only applied on the front end.
             *
             * @since 2.8.0
             *
             * @param string  $prepend Text displayed before the post title.
             *                         Default 'Protected: %s'.
             * @param WP_Post $post    Current post object.
             */
            $protected_title_format = apply_filters( 'protected_title_format', __( 'Protected: %s' ), $post );
            $title = sprintf( $protected_title_format, $title );
        } elseif ( isset( $post->post_status ) && 'private' == $post->post_status ) {

            /**
             * Filters the text prepended to the post title of private posts.
             *
             * The filter is only applied on the front end.
             *
             * @since 2.8.0
             *
             * @param string  $prepend Text displayed before the post title.
             *                         Default 'Private: %s'.
             * @param WP_Post $post    Current post object.
             */
            $private_title_format = apply_filters( 'private_title_format', __( 'Private: %s' ), $post );
            $title = sprintf( $private_title_format, $title );
        }
    }

    /**
     * Filters the post title.
     *
     * @since 0.71
     *
     * @param string $title The post title.
     * @param int    $id    The post ID.
     */
    return apply_filters( 'the_title', $title, $id );
}

/**
 * Display the Post Global Unique Identifier (guid).
 *
 * The guid will appear to be a link, but should not be used as a link to the
 * post. The reason you should not use it as a link, is because of moving the
 * blog across domains.
 *
 * URL is escaped to make it XML-safe.
 *
 * @since 1.5.0
 *
 * @param int|WP_Post $post Optional. Post ID or post object. Default is global $post.
 */
function the_guid( $post = 0 ) {
    $post = get_post( $post );

    $guid = isset( $post->guid ) ? get_the_guid( $post ) : '';
    $id   = isset( $post->ID ) ? $post->ID : 0;

    /**
     * Filters the escaped Global Unique Identifier (guid) of the post.
     *
     * @since 4.2.0
     *
     * @see get_the_guid()
     *
     * @param string $guid Escaped Global Unique Identifier (guid) of the post.
     * @param int    $id   The post ID.
     */
    echo apply_filters( 'the_guid', $guid, $id );
}

/**
 * Retrieve the Post Global Unique Identifier (guid).
 *
 * The guid will appear to be a link, but should not be used as an link to the
 * post. The reason you should not use it as a link, is because of moving the
 * blog across domains.
 *
 * @since 1.5.0
 *
 * @param int|WP_Post $post Optional. Post ID or post object. Default is global $post.
 * @return string
 */
function get_the_guid( $post = 0 ) {
    $post = get_post( $post );

    $guid = isset( $post->guid ) ? $post->guid : '';
    $id   = isset( $post->ID ) ? $post->ID : 0;

    /**
     * Filters the Global Unique Identifier (guid) of the post.
     *
     * @since 1.5.0
     *
     * @param string $guid Global Unique Identifier (guid) of the post.
     * @param int    $id   The post ID.
     */
    return apply_filters( 'get_the_guid', $guid, $id );
}

/**
 * Display the post content.
 *
 * @since 0.71
 *
 * @param string $more_link_text Optional. Content for when there is more text.
 * @param bool   $strip_teaser   Optional. Strip teaser content before the more text. Default is false.
 */
function the_content( $more_link_text = null, $strip_teaser = false) {
    $content = get_the_content( $more_link_text, $strip_teaser );

    /**
     * Filters the post content.
     *
     * @since 0.71
     *
     * @param string $content Content of the current post.
     */
    $content = apply_filters( 'the_content', $content );
    $content = str_replace( ']]>', ']]>', $content );
    echo $content;
}

/**
 * Retrieve the post content.
 *
 * @since 0.71
 *
 * @global int   $page      Page number of a single post/page.
 * @global int   $more      Boolean indicator for whether single post/page is being viewed.
 * @global bool  $preview   Whether post/page is in preview mode.
 * @global array $pages     Array of all pages in post/page. Each array element contains part of the content separated by the <!--nextpage--> tag.
 * @global int   $multipage Boolean indicator for whether multiple pages are in play.
 *
 * @param string $more_link_text Optional. Content for when there is more text.
 * @param bool   $strip_teaser   Optional. Strip teaser content before the more text. Default is false.
 * @return string
 */
function get_the_content( $more_link_text = null, $strip_teaser = false ) {
    global $page, $more, $preview, $pages, $multipage;

    $post = get_post();

    if ( null === $more_link_text ) {
        $more_link_text = sprintf(
            '<span aria-label="%1$s">%2$s</span>',
            sprintf(
                /* translators: %s: Name of current post */
                __( 'Continue reading %s' ),
                the_title_attribute( array( 'echo' => false ) )
            ),
            __( '(more…)' )
        );
    }

    $output = '';
    $has_teaser = false;

    // If post password required and it doesn't match the cookie.
    if ( post_password_required( $post ) )
        return get_the_password_form( $post );

    if ( $page > count( $pages ) ) // if the requested page doesn't exist
        $page = count( $pages ); // give them the highest numbered page that DOES exist

    $content = $pages[$page - 1];
    if ( preg_match( '/<!--more(.*?)?-->/', $content, $matches ) ) {
        $content = explode( $matches[0], $content, 2 );
        if ( ! empty( $matches[1] ) && ! empty( $more_link_text ) )
            $more_link_text = strip_tags( wp_kses_no_null( trim( $matches[1] ) ) );

        $has_teaser = true;
    } else {
        $content = array( $content );
    }

    if ( false !== strpos( $post->post_content, '<!--noteaser-->' ) && ( ! $multipage || $page == 1 ) )
        $strip_teaser = true;

    $teaser = $content[0];

    if ( $more && $strip_teaser && $has_teaser )
        $teaser = '';

    $output .= $teaser;

    if ( count( $content ) > 1 ) {
        if ( $more ) {
            $output .= '<span id="more-' . $post->ID . '"></span>' . $content[1];
        } else {
            if ( ! empty( $more_link_text ) )

                /**
                 * Filters the Read More link text.
                 *
                 * @since 2.8.0
                 *
                 * @param string $more_link_element Read More link element.
                 * @param string $more_link_text    Read More text.
                 */
                $output .= apply_filters( 'the_content_more_link', ' <a href="' . get_permalink() . "#more-{$post->ID}\" class=\"more-link\">$more_link_text</a>", $more_link_text );
            $output = force_balance_tags( $output );
        }
    }

    if ( $preview ) // Preview fix for JavaScript bug with foreign languages.
        $output =    preg_replace_callback( '/\%u([0-9A-F]{4})/', '_convert_urlencoded_to_entities', $output );

    return $output;
}

/**
 * Preview fix for JavaScript bug with foreign languages.
 *
 * @since 3.1.0
 * @access private
 *
 * @param array $match Match array from preg_replace_callback.
 * @return string
 */
function _convert_urlencoded_to_entities( $match ) {
    return '&#' . base_convert( $match[1], 16, 10 ) . ';';
}

/**
 * Display the post excerpt.
 *
 * @since 0.71
 */
function the_excerpt() {

    /**
     * Filters the displayed post excerpt.
     *
     * @since 0.71
     *
     * @see get_the_excerpt()
     *
     * @param string $post_excerpt The post excerpt.
     */
    echo apply_filters( 'the_excerpt', get_the_excerpt() );
}

/**
 * Retrieves the post excerpt.
 *
 * @since 0.71
 * @since 4.5.0 Introduced the `$post` parameter.
 *
 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
 * @return string Post excerpt.
 */
function get_the_excerpt( $post = null ) {
    if ( is_bool( $post ) ) {
        _deprecated_argument( __FUNCTION__, '2.3.0' );
    }

    $post = get_post( $post );
    if ( empty( $post ) ) {
        return '';
    }

    if ( post_password_required( $post ) ) {
        return __( 'There is no excerpt because this is a protected post.' );
    }

    /**
     * Filters the retrieved post excerpt.
     *
     * @since 1.2.0
     * @since 4.5.0 Introduced the `$post` parameter.
     *
     * @param string $post_excerpt The post excerpt.
     * @param WP_Post $post Post object.
     */
    return apply_filters( 'get_the_excerpt', $post->post_excerpt, $post );
}

/**
 * Whether the post has a custom excerpt.
 *
 * @since 2.3.0
 *
 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
 * @return bool True if the post has a custom excerpt, false otherwise.
 */
function has_excerpt( $post = 0 ) {
    $post = get_post( $post );
    return ( !empty( $post->post_excerpt ) );
}

/**
 * Display the classes for the post div.
 *
 * @since 2.7.0
 *
 * @param string|array $class   One or more classes to add to the class list.
 * @param int|WP_Post  $post_id Optional. Post ID or post object. Defaults to the global `$post`.
 */
function post_class( $class = '', $post_id = null ) {
    // Separates classes with a single space, collates classes for post DIV
    echo 'class="' . join( ' ', get_post_class( $class, $post_id ) ) . '"';
}

/**
 * Retrieves the classes for the post div as an array.
 *
 * The class names are many. If the post is a sticky, then the 'sticky'
 * class name. The class 'hentry' is always added to each post. If the post has a
 * post thumbnail, 'has-post-thumbnail' is added as a class. For each taxonomy that
 * the post belongs to, a class will be added of the format '{$taxonomy}-{$slug}' -
 * eg 'category-foo' or 'my_custom_taxonomy-bar'.
 *
 * The 'post_tag' taxonomy is a special
 * case; the class has the 'tag-' prefix instead of 'post_tag-'. All classes are
 * passed through the filter, {@see 'post_class'}, with the list of classes, followed by
 * $class parameter value, with the post ID as the last parameter.
 *
 * @since 2.7.0
 * @since 4.2.0 Custom taxonomy classes were added.
 *
 * @param string|array $class   One or more classes to add to the class list.
 * @param int|WP_Post  $post_id Optional. Post ID or post object.
 * @return array Array of classes.
 */
function get_post_class( $class = '', $post_id = null ) {
    $post = get_post( $post_id );

    $classes = array();

    if ( $class ) {
        if ( ! is_array( $class ) ) {
            $class = preg_split( '#\s+#', $class );
        }
        $classes = array_map( 'esc_attr', $class );
    } else {
        // Ensure that we always coerce class to being an array.
        $class = array();
    }

    if ( ! $post ) {
        return $classes;
    }

    $classes[] = 'post-' . $post->ID;
    if ( ! is_admin() )
        $classes[] = $post->post_type;
    $classes[] = 'type-' . $post->post_type;
    $classes[] = 'status-' . $post->post_status;

    // Post Format
    if ( post_type_supports( $post->post_type, 'post-formats' ) ) {
        $post_format = get_post_format( $post->ID );

        if ( $post_format && !is_wp_error($post_format) )
            $classes[] = 'format-' . sanitize_html_class( $post_format );
        else
            $classes[] = 'format-standard';
    }

    $post_password_required = post_password_required( $post->ID );

    // Post requires password.
    if ( $post_password_required ) {
        $classes[] = 'post-password-required';
    } elseif ( ! empty( $post->post_password ) ) {
        $classes[] = 'post-password-protected';
    }

    // Post thumbnails.
    if ( current_theme_supports( 'post-thumbnails' ) && has_post_thumbnail( $post->ID ) && ! is_attachment( $post ) && ! $post_password_required ) {
        $classes[] = 'has-post-thumbnail';
    }

    // sticky for Sticky Posts
    if ( is_sticky( $post->ID ) ) {
        if ( is_home() && ! is_paged() ) {
            $classes[] = 'sticky';
        } elseif ( is_admin() ) {
            $classes[] = 'status-sticky';
        }
    }

    // hentry for hAtom compliance
    $classes[] = 'hentry';

    // All public taxonomies
    $taxonomies = get_taxonomies( array( 'public' => true ) );
    foreach ( (array) $taxonomies as $taxonomy ) {
        if ( is_object_in_taxonomy( $post->post_type, $taxonomy ) ) {
            foreach ( (array) get_the_terms( $post->ID, $taxonomy ) as $term ) {
                if ( empty( $term->slug ) ) {
                    continue;
                }

                $term_class = sanitize_html_class( $term->slug, $term->term_id );
                if ( is_numeric( $term_class ) || ! trim( $term_class, '-' ) ) {
                    $term_class = $term->term_id;
                }

                // 'post_tag' uses the 'tag' prefix for backward compatibility.
                if ( 'post_tag' == $taxonomy ) {
                    $classes[] = 'tag-' . $term_class;
                } else {
                    $classes[] = sanitize_html_class( $taxonomy . '-' . $term_class, $taxonomy . '-' . $term->term_id );
                }
            }
        }
    }

    $classes = array_map( 'esc_attr', $classes );

    /**
     * Filters the list of CSS classes for the current post.
     *
     * @since 2.7.0
     *
     * @param array $classes An array of post classes.
     * @param array $class   An array of additional classes added to the post.
     * @param int   $post_id The post ID.
     */
    $classes = apply_filters( 'post_class', $classes, $class, $post->ID );

    return array_unique( $classes );
}

/**
 * Display the classes for the body element.
 *
 * @since 2.8.0
 *
 * @param string|array $class One or more classes to add to the class list.
 */
function body_class( $class = '' ) {
    // Separates classes with a single space, collates classes for body element
    echo 'class="' . join( ' ', get_body_class( $class ) ) . '"';
}

/**
 * Retrieve the classes for the body element as an array.
 *
 * @since 2.8.0
 *
 * @global WP_Query $wp_query
 *
 * @param string|array $class One or more classes to add to the class list.
 * @return array Array of classes.
 */
function get_body_class( $class = '' ) {
    global $wp_query;

    $classes = array();

    if ( is_rtl() )
        $classes[] = 'rtl';

    if ( is_front_page() )
        $classes[] = 'home';
    if ( is_home() )
        $classes[] = 'blog';
    if ( is_archive() )
        $classes[] = 'archive';
    if ( is_date() )
        $classes[] = 'date';
    if ( is_search() ) {
        $classes[] = 'search';
        $classes[] = $wp_query->posts ? 'search-results' : 'search-no-results';
    }
    if ( is_paged() )
        $classes[] = 'paged';
    if ( is_attachment() )
        $classes[] = 'attachment';
    if ( is_404() )
        $classes[] = 'error404';

    if ( is_singular() ) {
        $post_id = $wp_query->get_queried_object_id();
        $post = $wp_query->get_queried_object();
        $post_type = $post->post_type;

        if ( is_page_template() ) {
            $classes[] = "{$post_type}-template";

            $template_slug  = get_page_template_slug( $post_id );
            $template_parts = explode( '/', $template_slug );

            foreach ( $template_parts as $part ) {
                $classes[] = "{$post_type}-template-" . sanitize_html_class( str_replace( array( '.', '/' ), '-', basename( $part, '.php' ) ) );
            }
            $classes[] = "{$post_type}-template-" . sanitize_html_class( str_replace( '.', '-', $template_slug ) );
        } else {
            $classes[] = "{$post_type}-template-default";
        }

        if ( is_single() ) {
            $classes[] = 'single';
            if ( isset( $post->post_type ) ) {
                $classes[] = 'single-' . sanitize_html_class( $post->post_type, $post_id );
                $classes[] = 'postid-' . $post_id;

                // Post Format
                if ( post_type_supports( $post->post_type, 'post-formats' ) ) {
                    $post_format = get_post_format( $post->ID );

                    if ( $post_format && !is_wp_error($post_format) )
                        $classes[] = 'single-format-' . sanitize_html_class( $post_format );
                    else
                        $classes[] = 'single-format-standard';
                }
            }
        }

        if ( is_attachment() ) {
            $mime_type = get_post_mime_type($post_id);
            $mime_prefix = array( 'application/', 'image/', 'text/', 'audio/', 'video/', 'music/' );
            $classes[] = 'attachmentid-' . $post_id;
            $classes[] = 'attachment-' . str_replace( $mime_prefix, '', $mime_type );
        } elseif ( is_page() ) {
            $classes[] = 'page';

            $page_id = $wp_query->get_queried_object_id();

            $post = get_post($page_id);

            $classes[] = 'page-id-' . $page_id;

            if ( get_pages( array( 'parent' => $page_id, 'number' => 1 ) ) ) {
                $classes[] = 'page-parent';
            }

            if ( $post->post_parent ) {
                $classes[] = 'page-child';
                $classes[] = 'parent-pageid-' . $post->post_parent;
            }
        }
    } elseif ( is_archive() ) {
        if ( is_post_type_archive() ) {
            $classes[] = 'post-type-archive';
            $post_type = get_query_var( 'post_type' );
            if ( is_array( $post_type ) )
                $post_type = reset( $post_type );
            $classes[] = 'post-type-archive-' . sanitize_html_class( $post_type );
        } elseif ( is_author() ) {
            $author = $wp_query->get_queried_object();
            $classes[] = 'author';
            if ( isset( $author->user_nicename ) ) {
                $classes[] = 'author-' . sanitize_html_class( $author->user_nicename, $author->ID );
                $classes[] = 'author-' . $author->ID;
            }
        } elseif ( is_category() ) {
            $cat = $wp_query->get_queried_object();
            $classes[] = 'category';
            if ( isset( $cat->term_id ) ) {
                $cat_class = sanitize_html_class( $cat->slug, $cat->term_id );
                if ( is_numeric( $cat_class ) || ! trim( $cat_class, '-' ) ) {
                    $cat_class = $cat->term_id;
                }

                $classes[] = 'category-' . $cat_class;
                $classes[] = 'category-' . $cat->term_id;
            }
        } elseif ( is_tag() ) {
            $tag = $wp_query->get_queried_object();
            $classes[] = 'tag';
            if ( isset( $tag->term_id ) ) {
                $tag_class = sanitize_html_class( $tag->slug, $tag->term_id );
                if ( is_numeric( $tag_class ) || ! trim( $tag_class, '-' ) ) {
                    $tag_class = $tag->term_id;
                }

                $classes[] = 'tag-' . $tag_class;
                $classes[] = 'tag-' . $tag->term_id;
            }
        } elseif ( is_tax() ) {
            $term = $wp_query->get_queried_object();
            if ( isset( $term->term_id ) ) {
                $term_class = sanitize_html_class( $term->slug, $term->term_id );
                if ( is_numeric( $term_class ) || ! trim( $term_class, '-' ) ) {
                    $term_class = $term->term_id;
                }

                $classes[] = 'tax-' . sanitize_html_class( $term->taxonomy );
                $classes[] = 'term-' . $term_class;
                $classes[] = 'term-' . $term->term_id;
            }
        }
    }

    if ( is_user_logged_in() )
        $classes[] = 'logged-in';

    if ( is_admin_bar_showing() ) {
        $classes[] = 'admin-bar';
        $classes[] = 'no-customize-support';
    }

    if ( get_background_color() !== get_theme_support( 'custom-background', 'default-color' ) || get_background_image() )
        $classes[] = 'custom-background';

    if ( has_custom_logo() ) {
        $classes[] = 'wp-custom-logo';
    }

    $page = $wp_query->get( 'page' );

    if ( ! $page || $page < 2 )
        $page = $wp_query->get( 'paged' );

    if ( $page && $page > 1 && ! is_404() ) {
        $classes[] = 'paged-' . $page;

        if ( is_single() )
            $classes[] = 'single-paged-' . $page;
        elseif ( is_page() )
            $classes[] = 'page-paged-' . $page;
        elseif ( is_category() )
            $classes[] = 'category-paged-' . $page;
        elseif ( is_tag() )
            $classes[] = 'tag-paged-' . $page;
        elseif ( is_date() )
            $classes[] = 'date-paged-' . $page;
        elseif ( is_author() )
            $classes[] = 'author-paged-' . $page;
        elseif ( is_search() )
            $classes[] = 'search-paged-' . $page;
        elseif ( is_post_type_archive() )
            $classes[] = 'post-type-paged-' . $page;
    }

    if ( ! empty( $class ) ) {
        if ( !is_array( $class ) )
            $class = preg_split( '#\s+#', $class );
        $classes = array_merge( $classes, $class );
    } else {
        // Ensure that we always coerce class to being an array.
        $class = array();
    }

    $classes = array_map( 'esc_attr', $classes );

    /**
     * Filters the list of CSS body classes for the current post or page.
     *
     * @since 2.8.0
     *
     * @param array $classes An array of body classes.
     * @param array $class   An array of additional classes added to the body.
     */
    $classes = apply_filters( 'body_class', $classes, $class );

    return array_unique( $classes );
}

/**
 * Whether post requires password and correct password has been provided.
 *
 * @since 2.7.0
 *
 * @param int|WP_Post|null $post An optional post. Global $post used if not provided.
 * @return bool false if a password is not required or the correct password cookie is present, true otherwise.
 */
function post_password_required( $post = null ) {
    $post = get_post($post);

    if ( empty( $post->post_password ) ) {
        /** This filter is documented in wp-includes/post-template.php */
        return apply_filters( 'post_password_required', false, $post );
    }

    if ( ! isset( $_COOKIE[ 'wp-postpass_' . COOKIEHASH ] ) ) {
        /** This filter is documented in wp-includes/post-template.php */
        return apply_filters( 'post_password_required', true, $post );
    }

    require_once ABSPATH . WPINC . '/class-phpass.php';
    $hasher = new PasswordHash( 8, true );

    $hash = wp_unslash( $_COOKIE[ 'wp-postpass_' . COOKIEHASH ] );
    if ( 0 !== strpos( $hash, '$P$B' ) ) {
        $required = true;
    } else {
        $required = ! $hasher->CheckPassword( $post->post_password, $hash );
    }

    /**
     * Filters whether a post requires the user to supply a password.
     *
     * @since 4.7.0
     *
     * @param bool    $required Whether the user needs to supply a password. True if password has not been
     *                          provided or is incorrect, false if password has been supplied or is not required.
     * @param WP_Post $post     Post data.
     */
    return apply_filters( 'post_password_required', $required, $post );
}

//
// Page Template Functions for usage in Themes
//

/**
 * The formatted output of a list of pages.
 *
 * Displays page links for paginated posts (i.e. includes the <!--nextpage-->.
 * Quicktag one or more times). This tag must be within The Loop.
 *
 * @since 1.2.0
 *
 * @global int $page
 * @global int $numpages
 * @global int $multipage
 * @global int $more
 *
 * @param string|array $args {
 *     Optional. Array or string of default arguments.
 *
 *     @type string       $before           HTML or text to prepend to each link. Default is `<p> Pages:`.
 *     @type string       $after            HTML or text to append to each link. Default is `</p>`.
 *     @type string       $link_before      HTML or text to prepend to each link, inside the `<a>` tag.
 *                                          Also prepended to the current item, which is not linked. Default empty.
 *     @type string       $link_after       HTML or text to append to each Pages link inside the `<a>` tag.
 *                                          Also appended to the current item, which is not linked. Default empty.
 *     @type string       $next_or_number   Indicates whether page numbers should be used. Valid values are number
 *                                          and next. Default is 'number'.
 *     @type string       $separator        Text between pagination links. Default is ' '.
 *     @type string       $nextpagelink     Link text for the next page link, if available. Default is 'Next Page'.
 *     @type string       $previouspagelink Link text for the previous page link, if available. Default is 'Previous Page'.
 *     @type string       $pagelink         Format string for page numbers. The % in the parameter string will be
 *                                          replaced with the page number, so 'Page %' generates "Page 1", "Page 2", etc.
 *                                          Defaults to '%', just the page number.
 *     @type int|bool     $echo             Whether to echo or not. Accepts 1|true or 0|false. Default 1|true.
 * }
 * @return string Formatted output in HTML.
 */
function wp_link_pages( $args = '' ) {
    global $page, $numpages, $multipage, $more;

    $defaults = array(
        'before'           => '<p>' . __( 'Pages:' ),
        'after'            => '</p>',
        'link_before'      => '',
        'link_after'       => '',
        'next_or_number'   => 'number',
        'separator'        => ' ',
        'nextpagelink'     => __( 'Next page' ),
        'previouspagelink' => __( 'Previous page' ),
        'pagelink'         => '%',
        'echo'             => 1
    );

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

    /**
     * Filters the arguments used in retrieving page links for paginated posts.
     *
     * @since 3.0.0
     *
     * @param array $params An array of arguments for page links for paginated posts.
     */
    $r = apply_filters( 'wp_link_pages_args', $params );

    $output = '';
    if ( $multipage ) {
        if ( 'number' == $r['next_or_number'] ) {
            $output .= $r['before'];
            for ( $i = 1; $i <= $numpages; $i++ ) {
                $link = $r['link_before'] . str_replace( '%', $i, $r['pagelink'] ) . $r['link_after'];
                if ( $i != $page || ! $more && 1 == $page ) {
                    $link = _wp_link_page( $i ) . $link . '</a>';
                }
                /**
                 * Filters the HTML output of individual page number links.
                 *
                 * @since 3.6.0
                 *
                 * @param string $link The page number HTML output.
                 * @param int    $i    Page number for paginated posts' page links.
                 */
                $link = apply_filters( 'wp_link_pages_link', $link, $i );

                // Use the custom links separator beginning with the second link.
                $output .= ( 1 === $i ) ? ' ' : $r['separator'];
                $output .= $link;
            }
            $output .= $r['after'];
        } elseif ( $more ) {
            $output .= $r['before'];
            $prev = $page - 1;
            if ( $prev > 0 ) {
                $link = _wp_link_page( $prev ) . $r['link_before'] . $r['previouspagelink'] . $r['link_after'] . '</a>';

                /** This filter is documented in wp-includes/post-template.php */
                $output .= apply_filters( 'wp_link_pages_link', $link, $prev );
            }
            $next = $page + 1;
            if ( $next <= $numpages ) {
                if ( $prev ) {
                    $output .= $r['separator'];
                }
                $link = _wp_link_page( $next ) . $r['link_before'] . $r['nextpagelink'] . $r['link_after'] . '</a>';

                /** This filter is documented in wp-includes/post-template.php */
                $output .= apply_filters( 'wp_link_pages_link', $link, $next );
            }
            $output .= $r['after'];
        }
    }

    /**
     * Filters the HTML output of page links for paginated posts.
     *
     * @since 3.6.0
     *
     * @param string $output HTML output of paginated posts' page links.
     * @param array  $args   An array of arguments.
     */
    $html = apply_filters( 'wp_link_pages', $output, $args );

    if ( $r['echo'] ) {
        echo $html;
    }
    return $html;
}

/**
 * Helper function for wp_link_pages().
 *
 * @since 3.1.0
 * @access private
 *
 * @global WP_Rewrite $wp_rewrite
 *
 * @param int $i Page number.
 * @return string Link.
 */
function _wp_link_page( $i ) {
    global $wp_rewrite;
    $post = get_post();
    $query_args = array();

    if ( 1 == $i ) {
        $url = get_permalink();
    } else {
        if ( '' == get_option('permalink_structure') || in_array($post->post_status, array('draft', 'pending')) )
            $url = add_query_arg( 'page', $i, get_permalink() );
        elseif ( 'page' == get_option('show_on_front') && get_option('page_on_front') == $post->ID )
            $url = trailingslashit(get_permalink()) . user_trailingslashit("$wp_rewrite->pagination_base/" . $i, 'single_paged');
        else
            $url = trailingslashit(get_permalink()) . user_trailingslashit($i, 'single_paged');
    }

    if ( is_preview() ) {

        if ( ( 'draft' !== $post->post_status ) && isset( $_GET['preview_id'], $_GET['preview_nonce'] ) ) {
            $query_args['preview_id'] = wp_unslash( $_GET['preview_id'] );
            $query_args['preview_nonce'] = wp_unslash( $_GET['preview_nonce'] );
        }

        $url = get_preview_post_link( $post, $query_args, $url );
    }

    return '<a href="' . esc_url( $url ) . '">';
}

//
// Post-meta: Custom per-post fields.
//

/**
 * Retrieve post custom meta data field.
 *
 * @since 1.5.0
 *
 * @param string $key Meta data key name.
 * @return false|string|array Array of values or single value, if only one element exists. False will be returned if key does not exist.
 */
function post_custom( $key = '' ) {
    $custom = get_post_custom();

    if ( !isset( $custom[$key] ) )
        return false;
    elseif ( 1 == count($custom[$key]) )
        return $custom[$key][0];
    else
        return $custom[$key];
}

/**
 * Display list of post custom fields.
 *
 * @since 1.2.0
 *
 * @internal This will probably change at some point...
 *
 */
function the_meta() {
    if ( $keys = get_post_custom_keys() ) {
        echo "<ul class='post-meta'>\n";
        foreach ( (array) $keys as $key ) {
            $keyt = trim( $key );
            if ( is_protected_meta( $keyt, 'post' ) ) {
                continue;
            }

            $values = array_map( 'trim', get_post_custom_values( $key ) );
            $value = implode( $values, ', ' );

            $html = sprintf( "<li><span class='post-meta-key'>%s</span> %s</li>\n",
                /* translators: %s: Post custom field name */
                sprintf( _x( '%s:', 'Post custom field name' ), $key ),
                $value
            );

            /**
             * Filters the HTML output of the li element in the post custom fields list.
             *
             * @since 2.2.0
             *
             * @param string $html  The HTML output for the li element.
             * @param string $key   Meta key.
             * @param string $value Meta value.
             */
            echo apply_filters( 'the_meta_key', $html, $key, $value );
        }
        echo "</ul>\n";
    }
}

//
// Pages
//

/**
 * Retrieve or display list of pages as a dropdown (select list).
 *
 * @since 2.1.0
 * @since 4.2.0 The `$value_field` argument was added.
 * @since 4.3.0 The `$class` argument was added.
 *
 * @param array|string $args {
 *     Optional. Array or string of arguments to generate a pages drop-down element.
 *
 *     @type int          $depth                 Maximum depth. Default 0.
 *     @type int          $child_of              Page ID to retrieve child pages of. Default 0.
 *     @type int|string   $selected              Value of the option that should be selected. Default 0.
 *     @type bool|int     $echo                  Whether to echo or return the generated markup. Accepts 0, 1,
 *                                               or their bool equivalents. Default 1.
 *     @type string       $name                  Value for the 'name' attribute of the select element.
 *                                               Default 'page_id'.
 *     @type string       $id                    Value for the 'id' attribute of the select element.
 *     @type string       $class                 Value for the 'class' attribute of the select element. Default: none.
 *                                               Defaults to the value of `$name`.
 *     @type string       $show_option_none      Text to display for showing no pages. Default empty (does not display).
 *     @type string       $show_option_no_change Text to display for "no change" option. Default empty (does not display).
 *     @type string       $option_none_value     Value to use when no page is selected. Default empty.
 *     @type string       $value_field           Post field used to populate the 'value' attribute of the option
 *                                               elements. Accepts any valid post field. Default 'ID'.
 * }
 * @return string HTML content, if not displaying.
 */
function wp_dropdown_pages( $args = '' ) {
    $defaults = array(
        'depth' => 0, 'child_of' => 0,
        'selected' => 0, 'echo' => 1,
        'name' => 'page_id', 'id' => '',
        'class' => '',
        'show_option_none' => '', 'show_option_no_change' => '',
        'option_none_value' => '',
        'value_field' => 'ID',
    );

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

    $pages = get_pages( $r );
    $output = '';
    // Back-compat with old system where both id and name were based on $name argument
    if ( empty( $r['id'] ) ) {
        $r['id'] = $r['name'];
    }

    if ( ! empty( $pages ) ) {
        $class = '';
        if ( ! empty( $r['class'] ) ) {
            $class = " class='" . esc_attr( $r['class'] ) . "'";
        }

        $output = "<select name='" . esc_attr( $r['name'] ) . "'" . $class . " id='" . esc_attr( $r['id'] ) . "'>\n";
        if ( $r['show_option_no_change'] ) {
            $output .= "\t<option value=\"-1\">" . $r['show_option_no_change'] . "</option>\n";
        }
        if ( $r['show_option_none'] ) {
            $output .= "\t<option value=\"" . esc_attr( $r['option_none_value'] ) . '">' . $r['show_option_none'] . "</option>\n";
        }
        $output .= walk_page_dropdown_tree( $pages, $r['depth'], $r );
        $output .= "</select>\n";
    }

    /**
     * Filters the HTML output of a list of pages as a drop down.
     *
     * @since 2.1.0
     * @since 4.4.0 `$r` and `$pages` added as arguments.
     *
     * @param string $output HTML output for drop down list of pages.
     * @param array  $r      The parsed arguments array.
     * @param array  $pages  List of WP_Post objects returned by `get_pages()`
      */
    $html = apply_filters( 'wp_dropdown_pages', $output, $r, $pages );

    if ( $r['echo'] ) {
        echo $html;
    }
    return $html;
}

/**
 * Retrieve or display list of pages (or hierarchical post type items) in list (li) format.
 *
 * @since 1.5.0
 * @since 4.7.0 Added the `item_spacing` argument.
 *
 * @see get_pages()
 *
 * @global WP_Query $wp_query
 *
 * @param array|string $args {
 *     Array or string of arguments. Optional.
 *
 *     @type int          $child_of     Display only the sub-pages of a single page by ID. Default 0 (all pages).
 *     @type string       $authors      Comma-separated list of author IDs. Default empty (all authors).
 *     @type string       $date_format  PHP date format to use for the listed pages. Relies on the 'show_date' parameter.
 *                                      Default is the value of 'date_format' option.
 *     @type int          $depth        Number of levels in the hierarchy of pages to include in the generated list.
 *                                      Accepts -1 (any depth), 0 (all pages), 1 (top-level pages only), and n (pages to
 *                                      the given n depth). Default 0.
 *     @type bool         $echo         Whether or not to echo the list of pages. Default true.
 *     @type string       $exclude      Comma-separated list of page IDs to exclude. Default empty.
 *     @type array        $include      Comma-separated list of page IDs to include. Default empty.
 *     @type string       $link_after   Text or HTML to follow the page link label. Default null.
 *     @type string       $link_before  Text or HTML to precede the page link label. Default null.
 *     @type string       $post_type    Post type to query for. Default 'page'.
 *     @type string|array $post_status  Comma-separated list or array of post statuses to include. Default 'publish'.
 *     @type string       $show_date    Whether to display the page publish or modified date for each page. Accepts
 *                                      'modified' or any other value. An empty value hides the date. Default empty.
 *     @type string       $sort_column  Comma-separated list of column names to sort the pages by. Accepts 'post_author',
 *                                      'post_date', 'post_title', 'post_name', 'post_modified', 'post_modified_gmt',
 *                                      'menu_order', 'post_parent', 'ID', 'rand', or 'comment_count'. Default 'post_title'.
 *     @type string       $title_li     List heading. Passing a null or empty value will result in no heading, and the list
 *                                      will not be wrapped with unordered list `<ul>` tags. Default 'Pages'.
 *     @type string       $item_spacing Whether to preserve whitespace within the menu's HTML. Accepts 'preserve' or 'discard'.
 *                                      Default 'preserve'.
 *     @type Walker       $walker       Walker instance to use for listing pages. Default empty (Walker_Page).
 * }
 * @return string|void HTML list of pages.
 */
function wp_list_pages( $args = '' ) {
    $defaults = array(
        'depth'        => 0,
        'show_date'    => '',
        'date_format'  => get_option( 'date_format' ),
        'child_of'     => 0,
        'exclude'      => '',
        'title_li'     => __( 'Pages' ),
        'echo'         => 1,
        'authors'      => '',
        'sort_column'  => 'menu_order, post_title',
        'link_before'  => '',
        'link_after'   => '',
        'item_spacing' => 'preserve',
        'walker'       => '',
    );

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

    if ( ! in_array( $r['item_spacing'], array( 'preserve', 'discard' ), true ) ) {
        // invalid value, fall back to default.
        $r['item_spacing'] = $defaults['item_spacing'];
    }

    $output = '';
    $current_page = 0;

    // sanitize, mostly to keep spaces out
    $r['exclude'] = preg_replace( '/[^0-9,]/', '', $r['exclude'] );

    // Allow plugins to filter an array of excluded pages (but don't put a nullstring into the array)
    $exclude_array = ( $r['exclude'] ) ? explode( ',', $r['exclude'] ) : array();

    /**
     * Filters the array of pages to exclude from the pages list.
     *
     * @since 2.1.0
     *
     * @param array $exclude_array An array of page IDs to exclude.
     */
    $r['exclude'] = implode( ',', apply_filters( 'wp_list_pages_excludes', $exclude_array ) );

    // Query pages.
    $r['hierarchical'] = 0;
    $pages = get_pages( $r );

    if ( ! empty( $pages ) ) {
        if ( $r['title_li'] ) {
            $output .= '<li class="pagenav">' . $r['title_li'] . '<ul>';
        }
        global $wp_query;
        if ( is_page() || is_attachment() || $wp_query->is_posts_page ) {
            $current_page = get_queried_object_id();
        } elseif ( is_singular() ) {
            $queried_object = get_queried_object();
            if ( is_post_type_hierarchical( $queried_object->post_type ) ) {
                $current_page = $queried_object->ID;
            }
        }

        $output .= walk_page_tree( $pages, $r['depth'], $current_page, $r );

        if ( $r['title_li'] ) {
            $output .= '</ul></li>';
        }
    }

    /**
     * Filters the HTML output of the pages to list.
     *
     * @since 1.5.1
     * @since 4.4.0 `$pages` added as arguments.
     *
     * @see wp_list_pages()
     *
     * @param string $output HTML output of the pages list.
     * @param array  $r      An array of page-listing arguments.
     * @param array  $pages  List of WP_Post objects returned by `get_pages()`
     */
    $html = apply_filters( 'wp_list_pages', $output, $r, $pages );

    if ( $r['echo'] ) {
        echo $html;
    } else {
        return $html;
    }
}

/**
 * Displays or retrieves a list of pages with an optional home link.
 *
 * The arguments are listed below and part of the arguments are for wp_list_pages()} function.
 * Check that function for more info on those arguments.
 *
 * @since 2.7.0
 * @since 4.4.0 Added `menu_id`, `container`, `before`, `after`, and `walker` arguments.
 * @since 4.7.0 Added the `item_spacing` argument.
 *
 * @param array|string $args {
 *     Optional. Arguments to generate a page menu. See wp_list_pages() for additional arguments.
 *
 *     @type string          $sort_column  How to sort the list of pages. Accepts post column names.
 *                                         Default 'menu_order, post_title'.
 *     @type string          $menu_id      ID for the div containing the page list. Default is empty string.
 *     @type string          $menu_class   Class to use for the element containing the page list. Default 'menu'.
 *     @type string          $container    Element to use for the element containing the page list. Default 'div'.
 *     @type bool            $echo         Whether to echo the list or return it. Accepts true (echo) or false (return).
 *                                         Default true.
 *     @type int|bool|string $show_home    Whether to display the link to the home page. Can just enter the text
 *                                         you'd like shown for the home link. 1|true defaults to 'Home'.
 *     @type string          $link_before  The HTML or text to prepend to $show_home text. Default empty.
 *     @type string          $link_after   The HTML or text to append to $show_home text. Default empty.
 *     @type string          $before       The HTML or text to prepend to the menu. Default is '<ul>'.
 *     @type string          $after        The HTML or text to append to the menu. Default is '</ul>'.
 *     @type string          $item_spacing Whether to preserve whitespace within the menu's HTML. Accepts 'preserve' or 'discard'. Default 'discard'.
 *     @type Walker          $walker       Walker instance to use for listing pages. Default empty (Walker_Page).
 * }
 * @return string|void HTML menu
 */
function wp_page_menu( $args = array() ) {
    $defaults = array(
        'sort_column'  => 'menu_order, post_title',
        'menu_id'      => '',
        'menu_class'   => 'menu',
        'container'    => 'div',
        'echo'         => true,
        'link_before'  => '',
        'link_after'   => '',
        'before'       => '<ul>',
        'after'        => '</ul>',
        'item_spacing' => 'discard',
        'walker'       => '',
    );
    $args = wp_parse_args( $args, $defaults );

    if ( ! in_array( $args['item_spacing'], array( 'preserve', 'discard' ) ) ) {
        // invalid value, fall back to default.
        $args['item_spacing'] = $defaults['item_spacing'];
    }

    if ( 'preserve' === $args['item_spacing'] ) {
        $t = "\t";
        $n = "\n";
    } else {
        $t = '';
        $n = '';
    }

    /**
     * Filters the arguments used to generate a page-based menu.
     *
     * @since 2.7.0
     *
     * @see wp_page_menu()
     *
     * @param array $args An array of page menu arguments.
     */
    $args = apply_filters( 'wp_page_menu_args', $args );

    $menu = '';

    $list_args = $args;

    // Show Home in the menu
    if ( ! empty($args['show_home']) ) {
        if ( true === $args['show_home'] || '1' === $args['show_home'] || 1 === $args['show_home'] )
            $text = __('Home');
        else
            $text = $args['show_home'];
        $class = '';
        if ( is_front_page() && !is_paged() )
            $class = 'class="current_page_item"';
        $menu .= '<li ' . $class . '><a href="' . home_url( '/' ) . '">' . $args['link_before'] . $text . $args['link_after'] . '</a></li>';
        // If the front page is a page, add it to the exclude list
        if (get_option('show_on_front') == 'page') {
            if ( !empty( $list_args['exclude'] ) ) {
                $list_args['exclude'] .= ',';
            } else {
                $list_args['exclude'] = '';
            }
            $list_args['exclude'] .= get_option('page_on_front');
        }
    }

    $list_args['echo'] = false;
    $list_args['title_li'] = '';
    $menu .= wp_list_pages( $list_args );

    $container = sanitize_text_field( $args['container'] );

    // Fallback in case `wp_nav_menu()` was called without a container.
    if ( empty( $container ) ) {
        $container = 'div';
    }

    if ( $menu ) {

        // wp_nav_menu doesn't set before and after
        if ( isset( $args['fallback_cb'] ) &&
            'wp_page_menu' === $args['fallback_cb'] &&
            'ul' !== $container ) {
            $args['before'] = "<ul>{$n}";
            $args['after'] = '</ul>';
        }

        $menu = $args['before'] . $menu . $args['after'];
    }

    $attrs = '';
    if ( ! empty( $args['menu_id'] ) ) {
        $attrs .= ' id="' . esc_attr( $args['menu_id'] ) . '"';
    }

    if ( ! empty( $args['menu_class'] ) ) {
        $attrs .= ' class="' . esc_attr( $args['menu_class'] ) . '"';
    }

    $menu = "<{$container}{$attrs}>" . $menu . "</{$container}>{$n}";

    /**
     * Filters the HTML output of a page-based menu.
     *
     * @since 2.7.0
     *
     * @see wp_page_menu()
     *
     * @param string $menu The HTML output.
     * @param array  $args An array of arguments.
     */
    $menu = apply_filters( 'wp_page_menu', $menu, $args );
    if ( $args['echo'] )
        echo $menu;
    else
        return $menu;
}

//
// Page helpers
//

/**
 * Retrieve HTML list content for page list.
 *
 * @uses Walker_Page to create HTML list content.
 * @since 2.1.0
 *
 * @param array $pages
 * @param int   $depth
 * @param int   $current_page
 * @param array $r
 * @return string
 */
function walk_page_tree( $pages, $depth, $current_page, $r ) {
    if ( empty($r['walker']) )
        $walker = new Walker_Page;
    else
        $walker = $r['walker'];

    foreach ( (array) $pages as $page ) {
        if ( $page->post_parent )
            $r['pages_with_children'][ $page->post_parent ] = true;
    }

    $args = array($pages, $depth, $r, $current_page);
    return call_user_func_array(array($walker, 'walk'), $args);
}

/**
 * Retrieve HTML dropdown (select) content for page list.
 *
 * @uses Walker_PageDropdown to create HTML dropdown content.
 * @since 2.1.0
 * @see Walker_PageDropdown::walk() for parameters and return description.
 *
 * @return string
 */
function walk_page_dropdown_tree() {
    $args = func_get_args();
    if ( empty($args[2]['walker']) ) // the user's options are the third parameter
        $walker = new Walker_PageDropdown;
    else
        $walker = $args[2]['walker'];

    return call_user_func_array(array($walker, 'walk'), $args);
}

//
// Attachments
//

/**
 * Display an attachment page link using an image or icon.
 *
 * @since 2.0.0
 *
 * @param int|WP_Post $id Optional. Post ID or post object.
 * @param bool        $fullsize     Optional, default is false. Whether to use full size.
 * @param bool        $deprecated   Deprecated. Not used.
 * @param bool        $permalink    Optional, default is false. Whether to include permalink.
 */
function the_attachment_link( $id = 0, $fullsize = false, $deprecated = false, $permalink = false ) {
    if ( !empty( $deprecated ) )
        _deprecated_argument( __FUNCTION__, '2.5.0' );

    if ( $fullsize )
        echo wp_get_attachment_link($id, 'full', $permalink);
    else
        echo wp_get_attachment_link($id, 'thumbnail', $permalink);
}

/**
 * Retrieve an attachment page link using an image or icon, if possible.
 *
 * @since 2.5.0
 * @since 4.4.0 The `$id` parameter can now accept either a post ID or `WP_Post` object.
 *
 * @param int|WP_Post  $id        Optional. Post ID or post object.
 * @param string|array $size      Optional. Image size. Accepts any valid image size, or an array
 *                                of width and height values in pixels (in that order).
 *                                Default 'thumbnail'.
 * @param bool         $permalink Optional, Whether to add permalink to image. Default false.
 * @param bool         $icon      Optional. Whether the attachment is an icon. Default false.
 * @param string|false $text      Optional. Link text to use. Activated by passing a string, false otherwise.
 *                                Default false.
 * @param array|string $attr      Optional. Array or string of attributes. Default empty.
 * @return string HTML content.
 */
function wp_get_attachment_link( $id = 0, $size = 'thumbnail', $permalink = false, $icon = false, $text = false, $attr = '' ) {
    $_post = get_post( $id );

    if ( empty( $_post ) || ( 'attachment' !== $_post->post_type ) || ! $url = wp_get_attachment_url( $_post->ID ) ) {
        return __( 'Missing Attachment' );
    }

    if ( $permalink ) {
        $url = get_attachment_link( $_post->ID );
    }

    if ( $text ) {
        $link_text = $text;
    } elseif ( $size && 'none' != $size ) {
        $link_text = wp_get_attachment_image( $_post->ID, $size, $icon, $attr );
    } else {
        $link_text = '';
    }

    if ( '' === trim( $link_text ) ) {
        $link_text = $_post->post_title;
    }

    if ( '' === trim( $link_text ) ) {
        $link_text = esc_html( pathinfo( get_attached_file( $_post->ID ), PATHINFO_FILENAME ) );
    }
    /**
     * Filters a retrieved attachment page link.
     *
     * @since 2.7.0
     *
     * @param string       $link_html The page link HTML output.
     * @param int          $id        Post ID.
     * @param string|array $size      Size of the image. Image size or array of width and height values (in that order).
     *                                Default 'thumbnail'.
     * @param bool         $permalink Whether to add permalink to image. Default false.
     * @param bool         $icon      Whether to include an icon. Default false.
     * @param string|bool  $text      If string, will be link text. Default false.
     */
    return apply_filters( 'wp_get_attachment_link', "<a href='" . esc_url( $url ) . "'>$link_text</a>", $id, $size, $permalink, $icon, $text );
}

/**
 * Wrap attachment in paragraph tag before content.
 *
 * @since 2.0.0
 *
 * @param string $content
 * @return string
 */
function prepend_attachment($content) {
    $post = get_post();

    if ( empty($post->post_type) || $post->post_type != 'attachment' )
        return $content;

    if ( wp_attachment_is( 'video', $post ) ) {
        $meta = wp_get_attachment_metadata( get_the_ID() );
        $atts = array( 'src' => wp_get_attachment_url() );
        if ( ! empty( $meta['width'] ) && ! empty( $meta['height'] ) ) {
            $atts['width'] = (int) $meta['width'];
            $atts['height'] = (int) $meta['height'];
        }
        if ( has_post_thumbnail() ) {
            $atts['poster'] = wp_get_attachment_url( get_post_thumbnail_id() );
        }
        $p = wp_video_shortcode( $atts );
    } elseif ( wp_attachment_is( 'audio', $post ) ) {
        $p = wp_audio_shortcode( array( 'src' => wp_get_attachment_url() ) );
    } else {
        $p = '<p class="attachment">';
        // show the medium sized image representation of the attachment if available, and link to the raw file
        $p .= wp_get_attachment_link(0, 'medium', false);
        $p .= '</p>';
    }

    /**
     * Filters the attachment markup to be prepended to the post content.
     *
     * @since 2.0.0
     *
     * @see prepend_attachment()
     *
     * @param string $p The attachment HTML output.
     */
    $p = apply_filters( 'prepend_attachment', $p );

    return "$p\n$content";
}

//
// Misc
//

/**
 * Retrieve protected post password form content.
 *
 * @since 1.0.0
 *
 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
 * @return string HTML content for password form for password protected post.
 */
function get_the_password_form( $post = 0 ) {
    $post = get_post( $post );
    $label = 'pwbox-' . ( empty($post->ID) ? rand() : $post->ID );
    $output = '<form action="' . esc_url( site_url( 'wp-login.php?action=postpass', 'login_post' ) ) . '" class="post-password-form" method="post">
    <p>' . __( 'This content is password protected. To view it please enter your password below:' ) . '</p>
    <p><label for="' . $label . '">' . __( 'Password:' ) . ' <input name="post_password" id="' . $label . '" type="password" size="20" /></label> <input type="submit" name="Submit" value="' . esc_attr_x( 'Enter', 'post password form' ) . '" /></p></form>
    ';

    /**
     * Filters the HTML output for the protected post password form.
     *
     * If modifying the password field, please note that the core database schema
     * limits the password field to 20 characters regardless of the value of the
     * size attribute in the form input.
     *
     * @since 2.7.0
     *
     * @param string $output The password form HTML output.
     */
    return apply_filters( 'the_password_form', $output );
}

/**
 * Whether currently in a page template.
 *
 * This template tag allows you to determine if you are in a page template.
 * You can optionally provide a template name or array of template names
 * and then the check will be specific to that template.
 *
 * @since 2.5.0
 * @since 4.2.0 The `$template` parameter was changed to also accept an array of page templates.
 * @since 4.7.0 Now works with any post type, not just pages.
 *
 * @param string|array $template The specific template name or array of templates to match.
 * @return bool True on success, false on failure.
 */
function is_page_template( $template = '' ) {
    if ( ! is_singular() ) {
        return false;
    }

    $page_template = get_page_template_slug( get_queried_object_id() );

    if ( empty( $template ) )
        return (bool) $page_template;

    if ( $template == $page_template )
        return true;

    if ( is_array( $template ) ) {
        if ( ( in_array( 'default', $template, true ) && ! $page_template )
            || in_array( $page_template, $template, true )
        ) {
            return true;
        }
    }

    return ( 'default' === $template && ! $page_template );
}

/**
 * Get the specific template name for a given post.
 *
 * @since 3.4.0
 * @since 4.7.0 Now works with any post type, not just pages.
 *
 * @param int|WP_Post $post Optional. Post ID or WP_Post object. Default is global $post.
 * @return string|false Page template filename. Returns an empty string when the default page template
 *     is in use. Returns false if the post does not exist.
 */
function get_page_template_slug( $post = null ) {
    $post = get_post( $post );

    if ( ! $post ) {
        return false;
    }

    $template = get_post_meta( $post->ID, '_wp_page_template', true );

    if ( ! $template || 'default' == $template ) {
        return '';
    }

    return $template;
}

/**
 * Retrieve formatted date timestamp of a revision (linked to that revisions's page).
 *
 * @since 2.6.0
 *
 * @param int|object $revision Revision ID or revision object.
 * @param bool       $link     Optional, default is true. Link to revisions's page?
 * @return string|false i18n formatted datetimestamp or localized 'Current Revision'.
 */
function wp_post_revision_title( $revision, $link = true ) {
    if ( !$revision = get_post( $revision ) )
        return $revision;

    if ( !in_array( $revision->post_type, array( 'post', 'page', 'revision' ) ) )
        return false;

    /* translators: revision date format, see https://secure.php.net/date */
    $datef = _x( 'F j, Y @ H:i:s', 'revision date format' );
    /* translators: %s: revision date */
    $autosavef = __( '%s [Autosave]' );
    /* translators: %s: revision date */
    $currentf  = __( '%s [Current Revision]' );

    $date = date_i18n( $datef, strtotime( $revision->post_modified ) );
    if ( $link && current_user_can( 'edit_post', $revision->ID ) && $link = get_edit_post_link( $revision->ID ) )
        $date = "<a href='$link'>$date</a>";

    if ( !wp_is_post_revision( $revision ) )
        $date = sprintf( $currentf, $date );
    elseif ( wp_is_post_autosave( $revision ) )
        $date = sprintf( $autosavef, $date );

    return $date;
}

/**
 * Retrieve formatted date timestamp of a revision (linked to that revisions's page).
 *
 * @since 3.6.0
 *
 * @param int|object $revision Revision ID or revision object.
 * @param bool       $link     Optional, default is true. Link to revisions's page?
 * @return string|false gravatar, user, i18n formatted datetimestamp or localized 'Current Revision'.
 */
function wp_post_revision_title_expanded( $revision, $link = true ) {
    if ( !$revision = get_post( $revision ) )
        return $revision;

    if ( !in_array( $revision->post_type, array( 'post', 'page', 'revision' ) ) )
        return false;

    $author = get_the_author_meta( 'display_name', $revision->post_author );
    /* translators: revision date format, see https://secure.php.net/date */
    $datef = _x( 'F j, Y @ H:i:s', 'revision date format' );

    $gravatar = get_avatar( $revision->post_author, 24 );

    $date = date_i18n( $datef, strtotime( $revision->post_modified ) );
    if ( $link && current_user_can( 'edit_post', $revision->ID ) && $link = get_edit_post_link( $revision->ID ) )
        $date = "<a href='$link'>$date</a>";

    $revision_date_author = sprintf(
        /* translators: post revision title: 1: author avatar, 2: author name, 3: time ago, 4: date */
        __( '%1$s %2$s, %3$s ago (%4$s)' ),
        $gravatar,
        $author,
        human_time_diff( strtotime( $revision->post_modified ), current_time( 'timestamp' ) ),
        $date
    );

    /* translators: %s: revision date with author avatar */
    $autosavef = __( '%s [Autosave]' );
    /* translators: %s: revision date with author avatar */
    $currentf  = __( '%s [Current Revision]' );

    if ( !wp_is_post_revision( $revision ) )
        $revision_date_author = sprintf( $currentf, $revision_date_author );
    elseif ( wp_is_post_autosave( $revision ) )
        $revision_date_author = sprintf( $autosavef, $revision_date_author );

    /**
     * Filters the formatted author and date for a revision.
     *
     * @since 4.4.0
     *
     * @param string  $revision_date_author The formatted string.
     * @param WP_Post $revision             The revision object.
     * @param bool    $link                 Whether to link to the revisions page, as passed into
     *                                      wp_post_revision_title_expanded().
     */
    return apply_filters( 'wp_post_revision_title_expanded', $revision_date_author, $revision, $link );
}

/**
 * Display list of a post's revisions.
 *
 * Can output either a UL with edit links or a TABLE with diff interface, and
 * restore action links.
 *
 * @since 2.6.0
 *
 * @param int|WP_Post $post_id Optional. Post ID or WP_Post object. Default is global $post.
 * @param string      $type    'all' (default), 'revision' or 'autosave'
 */
function wp_list_post_revisions( $post_id = 0, $type = 'all' ) {
    if ( ! $post = get_post( $post_id ) )
        return;

    // $args array with (parent, format, right, left, type) deprecated since 3.6
    if ( is_array( $type ) ) {
        $type = ! empty( $type['type'] ) ? $type['type']  : $type;
        _deprecated_argument( __FUNCTION__, '3.6.0' );
    }

    if ( ! $revisions = wp_get_post_revisions( $post->ID ) )
        return;

    $rows = '';
    foreach ( $revisions as $revision ) {
        if ( ! current_user_can( 'read_post', $revision->ID ) )
            continue;

        $is_autosave = wp_is_post_autosave( $revision );
        if ( ( 'revision' === $type && $is_autosave ) || ( 'autosave' === $type && ! $is_autosave ) )
            continue;

        $rows .= "\t<li>" . wp_post_revision_title_expanded( $revision ) . "</li>\n";
    }

    echo "<div class='hide-if-js'><p>" . __( 'JavaScript must be enabled to use this feature.' ) . "</p></div>\n";

    echo "<ul class='post-revisions hide-if-no-js'>\n";
    echo $rows;
    echo "</ul>";
}