A new post to the SitePoint PHP Blog today (from Paul Annesley) looks briefly at how, with the help of XDebug, you can make your applications lighter and faster.

So we've got potentially slower code, and we can no longer just open up our simple PHP script and follow its execution from the top of the file to the bottom. How do we figure out exactly what's going on inside?

He doesn't go through the installation of XDebug, but he does give an example (complete with screenshots) of how to use it in conjunction with two other applications - WinCacheGrind for Windows users and KCachegrind - to work with the output XDebug produces.