title: Why I cannot get facebook like my page?
body: <p>What I want to do is user must like my page first then only can go to my <code>facebook apps</code>, but I have no idea why I cannot detect it and I had <code>var_dump</code> my page liked, result is <strong>NULL</strong></p>
  
  <p>here is my code</p>
  
  <pre><code>$request = $_REQUEST["signed_request"];
  list($encoded_sig, $load) = explode('.', $request, 2);
  $fbData = json_decode(base64_decode(strtr($load, '-_', '+/')), true);
  
  var_dump($fbData["page"]["liked"]);// output is NULL
  
  if (!empty($fbData["page"]["liked"]))
  { 
    echo "This content is for Fans only!";
  } else {
    echo "Please click on the Like button to view this tab!";
  }
  </code></pre>
  
  <p>Any idea how to do it?</p>