As you probably already know, there's a lot of debate over the internet about the right tool to serve as a PHP IDE. I, personally, have tested all of them and sticked with one from a long time ago. I was annoyed by the slowness of some editors and lack of tools on others. Not to mention about code completion for OOP, quick jump to declaration and all that stuff that saves a lot of precious time.
If you're still in the look for a good tool I would like to highlight some of the features of what we're using over here at drsoft. phpDesigner is a great tool for every PHP programmer. Judging by it's speed you would probably say that is a light IDE but that would be so wrong. I never seen so much features in one IDE from a long time. Here's a nice list that we've been putting together to highlight the most important parts of it, what we love most at this "ginsu knife" of PHP.
Code beautifier
Perform a code beautifier in just 2 mouse clicks. We're doing this all the time as we don't have the same way of writing PHP code. This tool allows us to write using our own style and transform everything to the standards in no time at all.
Code explorer
Have a short preview of your file with all the functions, classes and included or required files by using the code explorer view. This tool allows you to easily identify all the important stuff from your page.
Easy commenting
Select and comment large portions of code with 1 click. Pick from the many commenting styles available to comment exactly how you want.
Code completion
Get assistance as you type. No need to jump over to the declaration of a function to see what's all about. phpDesigner does that by itself.
Debugging
Code, test, run and debug your scripts from the same interface. No need for third party installs and heavy work.
Code libraries
Tired of always having to browse the online documentation to find PHP5 libraries? phpDesigner has this implemented in the "code libraries" window. All documented and ready to assist.
OOP support
This one is really helpful! OPP support for PHP frameworks (and it really works) or normal projects. PHP5 support as well.
PHPDocumentor wizard
With this addon you can document all your functions. libraries or files. There's also a PHPDocumentor wizard to generate html documentation for your project. Again, all in the same interface.
Smarty support
phpDesigner supports Smarty as well. Both in hihlighting and in adding the most popular functions from an easy to use drop-down.
Code snippets
Everybody uses code snippets! Where do you keep yours? Let phpDesigner store them and use them whenever, wherever you want with a smart drag and drop.