facebook php sdk - catch if user didnt give permissions (authentication failed)

Question

Documentation says: "redirect_uri - (optional) The URL to redirect the user to once the login/authorization process is complete. The user will be redirected to the URL on both login success and failure, so you must check the error parameters in the URL as described in the authentication documentation. If this property is not specified, the user will be redirected to the current URL (i.e. the URL of the page where this method was called, typically the current URL in the user's browser)." So there is a method to catch if user refused autnentication/permissions, but link to corresponding documentation doesnt exist anymore (https://developers.facebook.com/docs/authentication/).

For the simplicity, redirect_uri is same address as a starting php file, and the php code is as simple as:

require 'facebook.php';
$facebook = new Facebook(array(
  'appId'  => 'X',
  'secret' => 'Y',
));
$user = $facebook->getUser();
if ($user) {
  try {
    $user_profile = $facebook->api('/me');
  } catch (FacebookApiException $e) {
    error_log($e);
    $user = null;
  }
}
if (!$user) {
  $params = array(
    'scope' => 'read_stream, friends_likes',
    'redirect_uri' => 'http://myapp.com/app'
  );
  $loginUrl = $facebook->getLoginUrl($params);
}

Anybody knows how to catch that information?

Answer 1

You can do following to check the permissions:

$permissions = $facebook->api("/me/permissions");
if( array_key_exists('publish_stream', $permissions['data'][0]) ) {
    // Permission is granted!
    // Do the related task
    $post_id = $facebook->api('/me/feed', 'post', array('message'=>'Hello World!'));
} else {
    // We don't have the permission
    // Alert the user or ask for the permission!
    header( "Location: " . $facebook->getLoginUrl(array("scope" => "publish_stream")) );
}