public function run()
    {
        // The token or post data is invalid
        if ($this->parseRet['code'] !== 1) {
            return false;
        }

        // Output 'echostr' for first time authentication
        if (isset($this->query['echostr'])) {
            return htmlspecialchars($this->query['echostr'], ENT_QUOTES, 'UTF-8');
        }

        $msg = $this->handleMsg();
        if (!$msg) {
            return 'success';
        }
        return $this->isEncrypted() ? $this->encryptMsg($msg) : $msg;
    }