facebook Like check subscriber

I was reading the facebook API references. http://developers.facebook.com/docs/reference/javascript/FB.Event.subscribe/

My client wants some sort of competition but only wants the users to like the app, to enter for the competition.

The like button is generated by facebook, not us on our site or within the frame provided on the application so its an application like button.

So I was wondering if that page is the right page I am looking to achieve this, or even if thi开发者_开发百科s is possible, because I have no clue how to do this.

Hope this make some sense :)

You can do this on facebook itself. Not sure if you can do it on your own website. Google "fan gate" for more info.