auto login to other sites php script

I want a script by which i can login to other website without opening their login page.

The scenario is like this. I do not want to give login id and password to others. They just need to click a link or button and script will do its wor开发者_如何学Ck. It will pass the required login id and password and submit the login form and it is logged in. And client have all the credential.

I would never trust any site that requires me to enter my username and password for another site. How do I know you are not going to hack my account? Instead use OpenID. This way your users need to log in to the other site and give your site temporary access using a token. All of the major social networking sites support OpenID or similar.