I am trying to debug the registration form.
Is there an easy way to debug a page with message data accompanying a request?
If you want to debug the POST method on a PHP page, make sure that you have "Debug all pages" installed in Run-> Open Debug Dialog; PHP Web Page / New Configuration, Advanced Tab. Then you must allow a PHP script to display the web page with the form. When you put data in a form and submit it, the debugger will now allow you to debug this page with POST data.
Hope this helps.
Source: How to set up a free PHP debugger using Eclipse PDT + XDebug