Currently me and my friend are developing a website, for what we will call 'projects' we just have a basic auto increment id in the database used to navigate to projects such as

oururl.com/viewproject?id=1

but we started thinking, if we have alot of posted projects thats going to be a LONG url. So we need to somehow randomly generate a alphanumerical string about 6 characters long. We want the chance of the string being duplicated being extremely low and of course we will query the database before assigning an identifier. Thanks for anyhelp, means alot!