Best OS X IDE for working with WordPress?

I’m looking to replace the hodgepodge of editors and file transfer programs I use with an IDE. I do a lot with WordPress now, so whatever IDE is best for that would be of particular interest to me. I work almost exclusively on OS X (I test on Windows, but that’s all). I’m also primarily a professor (design & digital media, so I’m not out of my element here :-). The work I do with WordPress is mostly volunteer work for nonprofits.

I’ve found several good code editors, but they lack debugging ability. I hear that Komodo has good debugging, but only in the pro version and I can’t afford to buy that for volunteer work.

Does anyone have suggestions?

TIA,
Tery