/**
  * Check if the user the necessary credentials to see this particular item
  *
  * @param array $item
  * @param sfUser $user
  */
 public static function hasPermission($item, $user)
 {
     if (!$user->isAuthenticated()) {
         return false;
     }
     return isset($item['credentials']) ? $user->hasCredential($item['credentials']) : true;
 }