I'm using the Zend OpenID library found here. I see there is a demo up, which works beautifully, but I don't see any source included for login.php. When I bring the files into my local apache and try to replicate what I see by viewing the source in the demo, I see an interface. When trying to use one of the login options, I see it makes posts like
http://localhost/zfopenid/public/user/login?action=verify&openid_username=&openid_identifier=http%3A%2F%2Fopenid.aol.com%2F
so there is certainly some php involved in that login file that I'm not able to see. I tried including application/controllers/UserController.php, but I get
Fatal error: Class 'Zend_Controller_Action' not found in /var/www/zfopenid/application/controllers/UserController.php on line 3
I don't know this Zend OpenID library but it sounds interesting. The problem is, at first look, it is tightly integrated into the Zend Framework and not a stand alone library. You'll have to run it as ZF application or find the components and then try if you can use them.
UPDATE If you want to test the downloaded application you have to make the /public directory your web root directory and the index.php your default root file. Then you can open the demo yourself. Again if you like to integrate it into your project it will be difficult because for what I see so far there is code all over the place which makes it increasingly difficult if you want it as a stand alone application.