How to detect Facebook Like button pressed and trigger event?

Question

Here is the example:

• http://www.facebook.com/UEvents?v=app_4949752878&ref=ts

These guys get people to click on Like button (in Step 1) first bef

Answer 1

Actually information if user is page fan or not exists in signed request. Since you need firstly to decode signed request like it is here:

 $signed_request = $_REQUEST["signed_request"];
 list($encoded_sig, $payload) = explode('.', $signed_request, 2); 
 $data = json_decode(base64_decode(strtr($payload, '-_', '+/')), true);

And after that access page liked variable:

$pageLiked = $data['page']['liked'];

Now FB is on the way of deprecating FBML so don't consider as something that will work for a long base.