public function postMessages($queue_name, $messages, $properties = array())
    {
        $req = array(
            "messages" => array(),
        );
        foreach ($messages as $message) {
            $msg = new IronMQMessage($message, $properties);
            array_push($req['messages'], $msg->asArray());
        }
        $this->setJsonHeaders();
        $queue = rawurlencode($queue_name);
        $url = "projects/{$this->project_id}/queues/$queue/messages";
        $res = $this->apiCall(self::POST, $url, $req);
        return self::json_decode($res);
    }