I normally don't compose articles like this but, I think this is a significant leap for PHP IDE's especially since it's free and backed by many major corporations.

Ok, after some digging I found a killer little all-platform editor called JEdit (http://www.jedit.org) and it's awesome. Once you install this puppy, you can download dozens of plugins!

What I'm talking about is the Eclipse IDE. Until recently, it was meant to be an opensource IDE for Java developers built by IBM. Now it's becoming an IDE dejour supporting any language you can build a plugin for and guess what? Eclipse now has a PHP plugin and it looks promising especially since I develop on a MAC.

Here's a couple of URL's to get you started:
Eclipse home page
Xored PHP plugin

Checkem out and have fun.