OpenID Directed Identity/Identifier Selection in PHP

[betrayal]

I'm trying to implement an OpenID server in PHP that supports identifier selection (some call this directed identity, which is actually a more specific case of identifier selection). That is, a user can enter a generic URI as their OpenID identifier, log in, and choose what identifier to return to the OpenID consumer.For example, if a user enters mysite.com as their indentifier, after they log in they would be prompted to return one of two identifiers to the OpenID consumer (perhaps mysite.com/myusername or mysite.com/anon-ad83f38c98b98).The advantage of this system is that you have the option to either use a single identifier among many sites, or use unique identifiers for individual sites.Anyway