I have to say recompiling PHP from the sources and enabling JPEG support in gd took me awhile to figure out.
Somewhere especially configure --help should have stated that --with-jpeg-dir is MANDATORY if you want to have JPEG support. And even if you did so, it doesn't mean you'll get it. If it's wrongly configured, no error is going to be output, all you get is "no JPEG support". What's more confusing is when JPEG support is disabled phpinfo won't say "JPEG Support: disabled", but just omit the entry so you won't even realize something is wrong.
If you recompile PHP or gd, make sure:
- rm -f config.cache FIRST
- make clean (this helps A LOT), actually you can just delete modules/gd.*, and every *.o in ext/gd. this part actually gave me the best headache
- ./configure --with-jpeg-dir=/usr/lib OR any other directory which contains the BINARY library of libjpeg
- make, make install
phpinfo should now display jpeg support... good luck.
(you lucky guys who already have PHP 5 installed on your server... you don't have to go through all the mess I had)
