I have a UUID string that I want to use as my MySQL tables primary key, the UUID is a 32 character hexadecimal string (after \'-\' characters are stripped). Due to the fact
For most cases it is best to store UUIDs/GUIDs as BINARY(16). See these related StackOverflow questions:
The conversion can (and probably should) be done in MySQL instead of PHP so whether you're using a 32bit PHP client or 64bits doesn't matter a bit (pun intended :P)