OpenID Autologin Janrain Example in php

[Fluid]

I want my website to automatically detect if a user is logged into google. If they are, it checks the database to see if they are already registered. If they are registered, it logs them in to my site. Otherwise, it redirects them to the login page.I think it might be the experimental x-has-session but I've no idea how to implement it. I'm using the JanRain OpenID PHP Library.Responses appriciated!