PHP is a server-side scripting language and interpreter that is available on a wide range of platforms, including some versions of Apache, and Microsoft's Internet Information Server (IIS). The original program was called Personal Home Page Tools, which is where the initials PHP come from. There are also a few other definitions of the name, mostly thought up in retrospect. Some say that PHP is a recursive three letter acronym meaning, PHP Hypertext Pre-processor. Another generally accepted definition is Pre Hypertext Processor. The PHP script is embedded in the Web page, and interpreted on the server before being sent to the client who requested the page. PHP is open source, and may be downloaded from www.php.net.