protected function ipnPostDataCheck()
    {
        if (count($this->postData) < 1 || !array_key_exists('REFNOEXT', $this->postData)) {
            $this->debugMessage[] = 'IPN POST: MISSING CONTENT';
            $this->errorMessage[] = 'IPN POST: MISSING CONTENT';
            return false;
        }
        return true;
    }