My authentication system is very customized, I do certain things that are not normally done, right now I can register, and authenticate, and get the user identity from a session that I store.
My question is if I can do all of these with what I have build so far, is there a reason to use Zend_Auth? What I'm interested to know is if Zend_Auth really ads anything that I currently don't have.
So does Zend_Auth do anything other than Authenticating the user against a table, and remembering the identity of the user?
Zend_Auth won't build again a brand new concept of what Auth is. You can customize all the authentification process around a user by extending or reusing a Zend_Auth_Adapter.
The main "+" that it might add is the Zend_Acl integration that might help you to restrict the usage of some modules of your webapp to some users according to their role.