http://www.techiedesi.com/post/229-setup-xdebug-and-php5-with-eclipse-34-to-debug-your-php-website-at-runtime/page-1

This time we’re attacking a relatively tougher challenge – to setup a good debugger in your Eclipse IDE for debugging your PHP website or scripts at runtime. A good debugging tool that allows setting breakpoints in your code, helps you step into the code and watch variable values can be so handy and makes you more productive. If you are familiar with Microsoft Visual Studio debugger, you know how powerful a debugger can be. However, when it comes to PHP, we do not see the same trends towards using a powerful debugger. People manage without a debugger, mostly echo’ing variable output and using self made debug and log calls. This does not really have to be the case with PHP.

During the course of this tutorial, you’ll learn how to setup a very good debugging environment for PHP using XDebug, that allows just-in-time debugging and site-wide breakpoints. This tutorial is written based on a Microsoft Windows XP based installation, but the steps are same for any other platform as well.