public static function connect($db, $host = 'localhost', $port = 27017)
  {
    // TODO: Use MongoDB\Driver\Manager
    self::$cnxHandler = new \MongoClient($host.':'.$port);
    self::$db = self::$cnxHandler->$db;

    if (!self::$cnxHandler || !self::$db) {
      return false;
    } else {
      return true;
    }
  }