OpenID, a free, open-source framework for "single sign-on" across different Web sites and applications. The even better news? There already exist a bunch of PHP widgets that allow developers to easily integrate OpenID into a PHP application, and this article is going to show you how to use them. So what are you waiting for? Flip the page, and let's get going!

For those not familiar with the authentication method, he defines OpenID and shows how it can help with the "too many passwords, too many accounts" problem many users face. He uses the PHP OpenID Library and the Authentication::OpenID_Consumer PEAR package (as well as several other PEAR packages to help with the connections and message formatting). He builds two simple forms to use the service - one to authenticate a user and another to create a new account.