Sample for Edit Url for a FB Page Tab App

Question

I am implementing the edit url FB Page Tab App. But it needs the initialization which should happen when the app is added to a fanpage by the admin.

I am looking for the initial callback/notification to my app-url when the app is loaded on the fanpage. (I have looked at this already - http://developers.facebook.com/docs/authentication/signed_request/).

I am looking for a sample that shows the handling of the signed_request in this case, from the fan-page-load and what details are available/etc..

Thanks !

Answer 1

Here's a sample of handling the signed request:

function parse_signed_request($signed_request, $secret) {
  list($encoded_sig, $payload) = explode('.', $signed_request, 2); 

  // decode the data
  $sig = base64_url_decode($encoded_sig);
  $data = json_decode(base64_url_decode($payload), true);

  if (strtoupper($data['algorithm']) !== 'HMAC-SHA256') {
    error_log('Unknown algorithm. Expected HMAC-SHA256');
    return null;
  }

  // check sig
  $expected_sig = hash_hmac('sha256', $payload, $secret, $raw = true);
  if ($sig !== $expected_sig) {
    error_log('Bad Signed JSON signature!');
    return null;
  }

  return $data;
}

function base64_url_decode($input) {
  return base64_decode(strtr($input, '-_', '+/'));
}

in $data there will be a "page" object that has a "admin" boolean. This will tell you if the current user of the page tab application is an admin of the page that the app is a tab of.