I’ve been writing PHP for a rather long time, and up until just recently I did it the old school way – I used EditPlus (basically notepad with syntax highlighting). I give you Eclipse:

Downloads Page

I was recently introduced to this excellent development platform, and I haven’t looked back. Besides taking care of little things like completing matching braces and being able to double click on a function (even user defined) for its description or being able to tell if a method overrides a parent method, it also has a great CVS plug-in. I’m still actually just figuring that part out, but already it’s making programming a lot more enjoyable for me by taking away a lot of the “dirty work”. I highly recommend Eclipse to PHP developers.