What Is PHP?

PHP is a language that has outgrown its name. It was originally conceived as a set of macros to help coders maintain personal home pages, and its name grew from its purpose. Since then, PHP's capabilities have been extended, taking it beyond a set of utilities to a full-featured programming language, capable of managing huge database-driven online environments.

As PHP's capabilities have grown, so too has its popularity. According to NetCraft (http://www.netcraft.com), PHP was running on more than 1 million hosts in November 1999. As of September 2001, that figure had already risen to over 6 million hosts, and by October 2003 PHP was reportedly installed on almost 14 million hosts. According to SecuritySpace.com, PHP is the most popular Apache module available, beating mod_ssl, Perl, and FrontPage.

PHP is officially known as PHP: Hypertext Preprocessor. It is a server-side scripting language often written in an HTML context. Unlike an ordinary HTML page, a PHP script is not sent directly to a client by the server; instead, it is parsed by the PHP engine. HTML elements in the script are left alone, but PHP code is interpreted and executed. PHP code in a script can query databases, create images, read and write files, talk to remote servers—the possibilities are endless. The output from PHP code is combined with the HTML in the script and the result sent to the user.

PHP is also installed as a command-line application, making it an excellent tool for scripting on a server. Many system administrators now use PHP for the sort of automation that has been traditionally handled by Perl or shell scripting.