that would be a cool idea 'talkPHP php libary' or somthing, some good snippets there m8.
Heres a little script i found a few years ago whilst messing with Zend Studio, i found it in the 'snippets' section, its quite interesting and (for me anyway) abit of a brain teaser to understand whats goin on
Just to note i DID NOT write this script, i don't want credit, the guy who wrote this should get credit (although he hasn't provided any information apart from his online alias 'bigmweb') i just thought u guys would find it interesting.
its a funny, when i showed it to my friend he said 'there has to be some form of witch craft involved, it must have something to do with the black arts' to a certain point i agree, although i do know understand how it works (i think

)
basically it converts a string to a barcode (well as close to a barcode as your goin to get in php) and its 2 way, as the guy says in his commenting he personally uses it to pretty up his session id's, but im sure there are other uses.
link:
http://www.zend.com//code/codex.php?ozid=425&single=1