System functions available within PHP include creating, opening, reading from, writing to and closing files on the server, executing system commands, create directories and modify file permissions in pre-determined directories. PHP can receive and process data from forms, save data to files, send by email and output a response to the browser.
This section deals mainly with exploring the possibilities of combining PHP and MySQL. To check if PHP is setup to use MySQL on your server, look for a section on MySQL in the phpinfo file described earlier. The technical details of setting up MySQL on your system are covered comprehensively in various text books. See the "Source Code Books" link below for more information.
Style sheets are designed to bring some of the simplicity of word processing styles to HTML. You can define how certain sections of text and code will be displayed, even down to the font and size.
XML continues the separation of data from presentation, to the point that one XML stylesheet contains all the common HTML code and a separate CSS stylesheet contains the formatting code. The XML file itself only needs to contain the code that is specific to that page.