public function sentence($string, $delimiter = ' ', $option = \PINYIN_NO_TONE)
    {
        if (\is_int($delimiter)) {
            list($option, $delimiter) = array($delimiter, ' ');
        }

        return implode($delimiter, $this->convert($string, $option | \PINYIN_KEEP_PUNCTUATION | \PINYIN_KEEP_ENGLISH | \PINYIN_KEEP_NUMBER));
    }