PHPEclipse is an Eclipse plugin that turns Eclipse into a PHP IDE. I don't usually do PHP work, but a close friend of mine asked me to review his company's PHP-based website so I had to review a massive body of PHP code within only a few hours I could spare.
While any text editor can be used to write PHP code, mere text editors are not enough when you don't have much time to cover a lot of code. So installed PHPEclipse and found it to be really nice. It checks syntax and helps you trace and navigate call hierarchies easily. I haven't tried its debugging capabilities, but I was delighted enough with just the capabilities I used to recommend it to PHP developers.
BTW, I am not a PHP developer and I don't build websites for small businesses. It's not that that is not a respectable business. It's just that I don't like doing what millions of others developers can with adequate competence. Yes, I am a prima donna of sort.