Add Xdebug, a debugging extension for PHP:

The Xdebug extension helps you debugging your script by providing
a lot of valuable debug information.
The debug information that Xdebug can provide includes the following:

    * stack traces and function traces in error messages with:
          o full parameter display for user defined functions
          o function name, file name and line indications
          o support for member functions
    * memory allocation
    * protection for infinite recursions

Xdebug also provides:

    * profiling information for PHP scripts
    * code coverage analysis
    * capabilities to debug your scripts interactively with a debug client

(sborrill)