How to use Facebook's account to log on to your own website?

Urgent and urgent .... How do you use your Facebook account to log on to your own website?
is now in the foreign site, customer requirements to be able to use the Facebook account to log in, the wall to get the API interface, but see not quite understand, we have done similar functions, espcms? Facebook API ? PHP

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Facebook's OAuth authentication, API parameter documentation, demo all have, this is not difficult, whether the key can be safely studied.
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Php,js, there are many kinds of, you can download the official SDK files, there are ready-made landing instances.
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I've done it.

With QQ, Baidu OAuth login principle is similar, the domestic to open a VPN can visit Facebook.
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Is like QQ, Baidu as the first to create an application AH.
Links: Https://developers.facebook.com/apps
Get AppID and secret, fill in the site URL (Redirect_uri) you want to return,
After the user authenticates the authorization, he will return the information to that URI.
Those user information seems to be $user_profile this.

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