What is Xdebug?

Xdebug is a PHP extension that adds a step debugger, a profiler, PHPUnit code coverage; adds stack traces for Notices, Warnings, Errors, and Exceptions; and upgrades var_dump(). It's created and supported by Derick Rethans.

Who made this site?

Matt Stauffer, from Tighten, after streaming with Derick to learn about Xdebug.