protected static function _dump($string)
    {
        $es = ['0', 'x07', 'x08', 't', 'n', 'v', 'f', 'r'];
        $unescaped = '';
        $chars = str_split($string);
        foreach ($chars as $char) {
            if ($char === '') {
                continue;
            }
            $value = ord($char);
            if ($value >= 7 && $value <= 13) {
                $unescaped .= '\\' . $es[$value - 6];
            } elseif ($char === '"' || $char === '$' || $char === '\\') {
                $unescaped .= '\\' . $char;
            } else {
                $unescaped .= $char;
            }
        }
        return $unescaped;
    }