Recently I came across an app called CodeBug, a really nice PHP debugger for Mac. I find debugging PHP really painful within editors such as Vim or Emacs, so up until now I'd been stuck using the incredibly bloated PHPStorm.
On Emacs you can currently use Geben for debugging but I find it's install really painful and it's usage even more so. I figured it was worth knocking up an Emacs plugin that allows you to set breakpoints in Codebug.
You can find the repo here and it's been accepted to Mepla, so it can be installed via the package manager.
Update: Codebug have very nicely featured this plugin on their homepage.