Hi all,
About a month or so ago I asked what people did about php debugging and stuff, something I really wanted that ZDE offered (the client itself I don't like).  Several people responded and it sounded like there were a lot of error_log'ing and stuff, but nothing on par with a real debugger. 

With this in mind, I figured it was worth mentioning this project:  http://www.bluestatic.org/software/macgdbp/

It's a Cocoa based client for xdebug that code stepping and more.  More info can be found here:  http://www.tuaw.com/2008/06/16/macgdbp-kills-php-bugs-dead/

Hope this is helpful (and appropriate).

Clark Endrizzi