Justin Carmony has submitted a post from his blog today that looks at to of the major PHP IDEs - Zend Studio 6 and Eclipse PDT - and compares them on features and functionality.
I've been using Zend Studio (ZS) for the last two years. It is developed by Zend, the company behind PHP. The very first time I used it and it was able to auto-complete my custom PHP classes I was sold. With version 6 of Zend Studio, they integrated Zend Studio with Eclipse, a popular IDE framework. I've been mostly happy with the new version, where as in some areas I felt that things were took a step back.
He compares their ease of installation, how easy they make it to refactor your code, debuggers included, the editor environment itself and, of course, the integration with Zend Platform/Zend Framework.