Apparently, if you compile php5 from source, and then later wish to compile with libjpeg support, you may not end up with libjpeg support for gd. There’s some sort of weird bug with php5′s config cache.

The solution is easy: rm config.cache before ./configure – recommend following that up with a make clean just because it’s usually a good idea to make clean before recompiling something.

This should not happen? Damned right it shouldn’t, especially when you need PHP 5.2 on the triple. Googling won’t help you, Mr. Bond – Googling for this specific error leaves much to be desired. Until (hopefully) now.

The fix is so easy, even a caveman could do it:

yum install libc-client libc-client-devel

Do that, and Bob’s yer uncle.

Of course, there’s another problem apparently. If, when restarting Apache, you get the following…

Starting httpd: Syntax error on line 190 of /etc/httpd/conf/httpd.conf:
Cannot load /usr/lib/httpd/modules/libphp5.so into server:
/usr/lib/libc-client.so.0: undefined symbol: mm_dlog [FAILED]

…Then you’re using a version of CentOS with some sort of borked libc. In this case, you have two options. Either remove –with-imap from your PHP configuration (Do you *really* need it, even? Chances are you do not…) or compile libc-client as a shared library and point the configuration to your copy rather than the distribution’s.