private function addRule($append = true)
    {
        if (empty($this->current_word)) {
            return;
        }
        foreach ($this->current_UserAgent as $ua) {
            if ($append === true) {
                $this->rules[$ua][$this->current_directive][] = $this->current_word;
                continue;
            }
            $this->rules[$ua][$this->current_directive] = $this->current_word;
        }
    }