I was more interested in Semacode, because it looks somehow cooler than QR in my opinion. Unfortunately I wasn't able to find any free (beer and speech) PHP library to create these codes.

He did, however, find a Javascript port (from a C library) to harvest the logic from and create his own PHP class to handle the semacode creation. He notes that it's probably still a bit buggy but is offering it for download to whoever might want to mess around with it.