Adv. photo scripts

Not sure if I'm at the right place but here goes.... I'm trying to create a script that will let users upload photos. It is a high traffic site and I've been told its best to create a function that will generate a unique filename for a temp. file, put the temp file elsewhere on the server, and then use an (unlink???) function to delete the temp. file after it gets written to the d-base. How would I do that?