protected function isWhitespace(&$length)
    {
        static $whitespaces = [
            "\f" => true,
            "\n" => true,
            "\r" => true,
            "\t" => true,
            ' ' => true,
        ];

        $length = 1;
        return isset($whitespaces[$this->substring($length)]);
    }
protected function isWhitespace(&$length)
    {
        static $whitespaces = [
            "\f" => true,
            "\n" => true,
            "\r" => true,
            "\t" => true,
            ' ' => true,
        ];

        $length = 1;
        return isset($whitespaces[$this->substring($length)]);
    }
{@inheritdoc}