Since I have been struggling with this for forever and finally found an answer, here’s an attempt to spread the wealth knowledge around.

Blog: Compiling & installing Xdebug for PHP 5.2.5 (Entropy.ch build) on OS X 10.5

Just to give the web crawlers some more info, the error message was:

PHP Warning: PHP Startup: Unable to load dynamic library ‘/usr/local/php5/lib/php/extensions/no-debug-non-zts-20060613/xdebug.so’ – (null) in Unknown on line 0

The solution is to compile it manually as a 64-bit application like so:

CFLAGS=’-arch x86_64′ ./configure –enable-xdebug

Hope this helps someone out there.