Xdebug is de facto the only debugger AFAIK. The integration in Phpstorm is great.

http://codebugapp.com is a fantastic front-end for Xdebug. I get a lot of mileage out of this, not least because I only had to set it up once and now it works with whichever editor I'm trying out this week.

NuSphere is better than xdebug. It allows more actions and is generally better.

But I use xdebug and phpstorm. I find it better than netbeans. Search in netbeans is good, but the whole thing has a weird GUI and is slow.

Best bet is to try a bunch.

Xdebug and with phpstorm 9 you have inline display of the values held in that variable which you can expand with a click.

That is incredibly powerful (PyCharm has it as well).

xdebug and phpstorm is great.

Xdebug and Netbeans, tons of tutorials on how to set it up on google/youtube.

xdebug and Eclipse is good enough.

Configuration got a lot easier since the installation wizard has been introduced: http://xdebug.org/wizard.php

Codebug. Phenomenal Xdebug client.