There are a few out there... PHPed and ZendIDE are two that I'm looking at right now. I currently use TextPad because it has an option to save files as PC,UNIX, or MAC file formats and has all of the code highlighting I need.
PHPed is supposed to offer debuging abilities, Homesite offers ftp loading, and ZendIDE is supposed to be the granddaddy of them all, but I can't get it to run.
PHPed seems to want to only utilize a Windows PHP version, but I haven't played with it enough to know for sure. *it's still an Alpha version, so it might be coming along later.
Hope this helps. (oh, I didn't include the URL's but a Google search should turn them up on the first link or so)
Charlie