Actually Eclipse + PDT extension is exactly what you'd need if you go for all IDE goodies. Aptana just automates somewhat the installation process and offers some more features (mostly non-php related). Zend studio is the best php IDE IMHO, but costs money...
This topic is some months old but I'd like to inform people about an editor that I have been using recently: Sublime Text 2. It's not an IDE but is has great features and even more amazing performance (in terms of speed and stability). It comes with a huge amount of features that are similar to those in the software mentioned above.
I'd say give it a try, it has a free trial (no time restriction or any restriction for that matter)!
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