The best IDE for PHP in my opinion is Zend Studio (which itself is based on Eclipse PDT). Note that in this case "best" does not necessarily mean "good." It is slow and a bit buggy, but even so, it's still the best option for PHP programmers. I've tried a ton of PHP editors over the years and I haven't yet found one that works great.
Komodo IDE would be my second choice. My only problem with Komodo is that the autocomplete is not as good. With properly structured apps where you use phpDoc to document return types etc., it should be alright. But I work on a project that doesn't really do that and Komodo can't read across files to know that $user is a User object for example.
