About imap_open: to save people headaches
 

For no reason, using imap_open() (http://www.php.net/imap_open ; the entire imap extension: http://www.php.net/imap) on my host completely made the script crash with no error, even when error_reporting was set to E_ALL. Very, very long story short, it's a conflict between RedHat and PHP.

To fix it, ask your host to recompile PHP, including using --with-imap. If they say it's already compiled that way, ask them to recompile it anyway.

That should work and save you the many hours of pain that it took me.