Xoops Content Management System extensively uses php. This is a server-side scripting language for creating dynamic Web pages. You can create pages with PHP and HTML using both languages quite freely.

When a visitor opens the page, the server processes the PHP commands including querying a database and then sends the results to the visitor's browser, just as with ASP or ColdFusion. Unlike ASP or ColdFusion, however, PHP is Open Source and cross-platform.

PHP runs on Windows NT and many Unix versions, and it can be built as an Apache module and as a binary that can run as a CGI. When built as an Apache module, PHP is especially lightweight and speedy. Without any process creation overhead, it can return results quickly, but it doesn't require the tuning of mod_perl to keep your server's memory image small.

In addition to manipulating the content of your pages, PHP can also send HTTP headers. You can set cookies, manage authentication, and redirect users. It offers excellent connectivity and support to many databases such as SQL (and ODBC), and integration with various external libraries like Smarty that let you do everything from generating templates, PDF documents to parsing XML.