Gonzalo Ayuso has a new post to his site today showing how to use the recently released PHP support for the Google App Engine along with Silex to create a login provider.

Last week Google announced the PHP support for Google App Engine (GAE). PHPStorm, the great IDE for PHP development, also announced support for Google App Engine PHP. Because of that now is time to hack a little bit with this new toy. [...] To build a simple Silex application over Google App Engine is pretty straightforward (more info here). Because of that we’re going to go a little further. We are going to use the log-in framework provided by GAE to log-in with our Goggle account within our Silex application. In fact we can use the standard OAuth authentication process but Google provides a simple way to use our gmail account.

He includes the code showing what the end result will look like as well as what's needed for the "LoginProvider" class. He also creates an "Auth" class where most of the work is done - creating the login URL, redirecting the user and checking to see if the user is logged in. He's made a screencast of the full process so you can see the authentication flow as its happening.