PHP - HTML Preprocessor
Use PHP to Force a File Download
Use PHP and the Content-disposition HTTP header to force files to download that would normally open in the Web browser.
Include HTML in Many Documents Using PHP
Learn how to use PHP to include portions of HTML in multiple Web documents while only editing the portion once.
Getting Started with PHP
If you want to learn PHP, a great place to start is with this great tutorial on PHP. This introductory article will have you comfortable with PHP before you know it.