I was trying to compile php5 on OS X Tiger, and I kept running into a problem. I have libjpeg and libpng installed via fink. I gave the configure script the arguments --with-jpeg-dir=/sw/lib and --with-png-dir=/sw/lib but the script kept complaining that it could not find libjpeg or libpng. The right arguments to give were --with-jpeg-dir=/sw and --with-png-dir=/sw.