This article pretty much sums it up very very well.

Update Feb 2011

But a couple of things you should know if you are using a Mac.  This simply summarizes the main tasks you need to do and does not describe in detail how you setup your debugger etc.  I have also switched my IDE to Netbeans as it appears a more stable and quicker environment for PHP.  I have been an Eclipse Java developer since the inception of Eclipse, but I thought you may find this note interesting in regards to Netbeans.

  • Download your XDebug so files from http://code.activestate.com/komodo/remotedebugging/ and not from the XDebug site
  • Use the phpinfo to see if XDebug is installed in the XDebug section of the page
  • Make sure your PHP ini file has the following entries where zend_extension points to the xdebug.so you downloaded from Komodo:
    zend_extension=/Applications/XAMPP/xamppfiles/lib/php/php-5.3.1/extensions/no-debug-non-zts-20090626/xdebug.so
    xdebug.remote_enable=1
    xdebug.remote_handler=dbgp
    xdebug.remote_mode=req
    xdebug.remote_host=localhost
    xdebug.remote_port=9000