stackoverflow's implementation of openid for PHP

Question

How do I implement the same login system as stackoverflow?

Where anyone can login based on their existing username/passwords from other web applications like, google, paypal, facebook, twitter and much much more?

Answer 1

For .NET you may checkout DotNetOpenAuth, that's what SO uses to implement OpenId authentication. So add the NuGet and get started. And for the nice icons checkout openid-selector.

For PHP you may checkout this project.

Answer 2

There are many OpenId solutions. Here is a list.

http://openid.net/add-openid/add-getting-started/

http://openid.net/developers/libraries/

For nice looking UI as Darin Dimitrov said you need to go with

http://code.google.com/p/openid-selector/