I recently went through a hellish upgrade to Snow Leopard and had to reinstall all my macports.
When I emerged all the graphic imaging functions in a PHP project had died… no warnings, no error messages. After experimenting a bit I realized that the standard GD library wasn’t installed.
Apparently in Snow Leopard macports, GD library doesn’t come along with php5 by default! I remember it did it Leopard (correct me if i’m wrong) so this was a confusing problem.
Very easy to fix:
sudo port install php5-gd