I beat my head against this one for hours. A recompiled version of PHP 5.1.6 on OS X was simply not loading my php.ini, even though a valid file existed in the place specified by the –with-config-file-path configure setting (/etc), and no other php.ini files existed on the system.
Eventually, after many rebuilds, I downloaded a clean copy of the source, rebuilt from scratch and voila – it worked. however, changing it and recompiling prodiced the broken results again. make distclean and a rebuild made it ork again. So, if you’re seeing this problem, a clean recompile (don’t forget to use config.nice) should make it all work again.
I’m not sure if this is a PHP bug or not – is it meant to work?