Those who use their on hosting inside an iframefor Facebook Fan page, there is a mechanism to pass additional parameters to your iframe page if you need to create a deep URL.
A normal Fan page of Facebook would like this:
This Url will call your domain, say example.com inside the iframe to load the page.
Each time the iframe is loaded, Facebook do a POST to this iframe URL with some data which we can use to identify the status of the user, eg, whether the user already liked this page, or any other parameter is passed through the fan page url.
Facebook keep app_data variable for developers to pass additional parameters to your iframe page.
To retrieve this information, in PHP, use can use the following code:
Check my article hereto see how you can get the ‘like’ status using PHP
Courtesy: From various online sources