open id or single sign on like stackoverflow

I m very impressed with the idea of stackoverflow, the way they provide the options to login to the users is very easy for any user.开发者_JAVA技巧 And if I have to do the same thing in my website then how its going to be. what will be the coding structure and coding snippets for the same in php , mysql and javascript (ajax).

https://stackoverflow.com/users/login

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Here is a simple OpenID class, that provides some functionality. First, you need to register an OpenID URL, then, simply type your OpenID in form in openid-example.php and it will redirect you to your OpenID provider, just as you do it on StackOverflow. Then, after your confirmation, it will redirect you back with some personal information, which you can use on your site.