private function generateOptionsRecursively($pid = 0, $prefix = '')
    {
        $options = [];
        $records = $this->db->fetchAll('SELECT * FROM tl_news_category WHERE pid=? ORDER BY sorting', [$pid]);

        foreach ($records as $record) {
            $options[$record['id']] = $prefix . $record['title'];

            foreach ($this->generateOptionsRecursively($record['id'], $record['title'] . ' / ') as $k => $v) {
                $options[$k] = $v;
            }
        }

        return $options;
    }