Discover what you should expect from an integrated development environment (IDE), and compare the cost and benefits of seven popular IDE choices for PHP.
From the article:
An IDE provides a one-stop shop for your coding work. An IDE contains an editor in which you can edit the code, debug the code, view your code in a browser (often embedded), and check in and out of source code control. To support that functionality, an IDE has a set of features you don't find in a basic editor, such as Notepad or Vim. Again, you can extend editors to do a lot of these things, but IDEs have all this functionality in one tidy package
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On a related note, my friend is hard core php developers and he recommends Zend's Eclipse PHP IDE.