OpenID implementation in PHP

I am considering implementing OpenID on my website and I am having a hard time finding good resources for OpenID implementation in php. So far I have only found RPX but I don't want to depend on third party vendors. I want something similar to SO , can anyone point me in the right direction and can you also tell approximately how much time wi开发者_如何学Cll it take to implement OpenID on my web site.

What about Simple OpenID via php classes.org? http://www.phpclasses.org/browse/package/3290.html

Zend Framework's Zend_OpenId is a choice.