PHP began life as a simple little cgi wrapper written in Perl. The name of this first package was Personal Home Page Tools, which later became Personal Home Page Construction Kit.
Old name is Professional Home Pages (PHP) and new name is PHP Hypertext Pre-Processor.
A tool was written to easily embed SQL queries into web pages. It was basically another CGI wrapper that parsed SQL queries and made it easy to create forms and tables based on these queries. This tool was named FI (Form Interpreter).
PHP/FI version 2.0 is a complete rewrite of these two packages combined into a single program. It evolved to a simple programming language embedded inside HTML files. PHP eliminates the need for numerous small Perl cgi programs by allowing you to place simple scripts directly in your HTML files. This speeds up the overall performance of your web pages since the overhead of forking Perl several times has been eliminated. It also makes it easier to manage large web sites by placing all components of a web page in a single html file. By including support for various databases, it also makes it trivial to develop database enabled web pages. Many people find the embedded nature much easier to deal with than trying to create separate HTML and CGI files.
Now PHP/FI is renamed as PHP.