public function call($method, array $params = array(), $format = 'php')
    {
        $params['method']       = $method;
        $params['token_auth']   = $this->token;
        $params['format']       = $format;

        $data = $this->getConnection()->send($params);

        if ('php' === $format) {
            $object = unserialize($data);

            if (isset($object['result']) && 'error' === $object['result']) {
                throw new Exception($object['message']);
            }

            return $object;
        } else {
            return $data;
        }
    }