public function setSpamCheck($enable, $threshold = null, $post_to_url = null)
    {
        if ($enable instanceof SpamCheck) {
            $spam_check = $enable;
            $this->spam_check = $spam_check;
            return;
        }
        $this->spam_check = new SpamCheck($enable, $threshold, $post_to_url);
        return;
    }