I absolutely love StackOverflow\'s usage of OpenID for registration. How would I go about adding this to my site? It is PHP based. I went to openid.net and looked at the librari
Documentation and examples.
OpenID is great, but have one big disadvantage. Let's imagine that I'm having Google account and Yahoo account. I will login using Google and then I will try to login using Yahoo. And it will be different accounts; it's really difficult to remember what openID provider I was using for registration... So, be careful with OpenID on entertainment websites, but it is still ok for developers websites.
Check OpenId class from Zend Framework.
This tutorial was helpful for a previous project I worked on using PHP and OpenID. It has an example app.
http://devzone.zend.com/article/3581
(source: zend.com)