mod_top is a PHP extension that is able to monitor PHP 4.4.x and PHP 5.x based applications. Sounds cool. Unfortunately it seems there's no source available, but the FAQ says that mod_top is free.

Check out some of the screenshots to get an idea of what the output looks like. There's three simple steps to getting it up and running - installing the Lamp1701 libraries, installing the PHP Probe extension and, of course, running the software. Check out the project's page for more information including the downloads.