private static function escapeString($str)
    {
        if (strlen($str) === 0) {
            return $str;
        }

        $str = str_replace(array(
            "\r",
            "\t",
            "\\",
            "\$",
            "\v",
            "\e",
            "\f",
            "\""
        ), array(
            '\r',
            '\t',
            '\\\\',
            '\$',
            '\v',
            '\e',
            '\f',
            '\"'
        ), $str);

        $str = str_replace("\n", "\\n\"\n\"", $str);

        $result = '';
        $str = str_split($str, 1);
        foreach ($str as $chr) {
            if (!ctype_print($chr) && $chr !== "\n") {
                $result .= '\\' . decoct(ord($chr));
            } else {
                $result .= $chr;
            }
        }
        if (substr($result, -5) === "\\n\"\n\"") {
            $result = substr($result, 0, -5) . "\\n";
        }
        return $result;
    }