public function quote_identifier($str)
    {
        $start = $this->options['identifier_start'];
        $end   = $this->options['identifier_end'];
        $name  = array();

        foreach (explode('.', $str) as $elem) {
            $elem = str_replace(array($start, $end), '', $elem);
            $name[] = $start . $elem . $end;
        }

        return implode($name, '.');
    }