how to share data in face book

I had done face book connect in my site for users to log in. Me want a feature 开发者_如何转开发to post a comment automatically on user's face book wall,when users logged to my site . This message should be like

You are connected to "site name" and "url" of site.

How it is possible in codeigniter .

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Check this forum. Facebook Ignited is really easy and cool!