CI_Encrypt::_xor_decode PHP Method

    protected function _xor_decode($string, $key)
    {
        $string = $this->_xor_merge($string, $key);
        $dec = '';
        for ($i = 0, $l = strlen($string); $i < $l; $i++) {
            $dec .= $string[$i++] ^ $string[$i];
        }
        return $dec;
    }

$encryption->set_key(KEY);
// WRITE YOUR OWN COOKIE HERE!
$cookie = rawurldecode("DZyb3lI68zh+RBNg8C4M03TEJhMR4BBMzNWA1YUampWQ6UKaiUhG48rwkdfIs9DJYNQc8pZDniflInnUrQz1FbRxueQ3NLCahBBmrTuw8Ib7OL7ycm/IbuR81WEVrWpYOnQ4Z57/w21OCyVw42TjSkXkfWfN67veJr5630eTBA03vRbvLunZ9RLEuElqNrJu/H63yibCv8fyRWNnKs56i5OuU6Dso11O49k4fhxd008WTvsGliLxiErCkWwYfGfcjUA3V2Mh9mkrLk0YEKIbt3hbNXhAnGhIVIVJURhnmibqEFUacB1gP1GnbP2fQy3NpJt317n/3/sH+jH4lM+53IY1HOJh7n/J6RU9jqMr1hdeslDxFaV7SCuB4vPuO7SScec8063aae4808b195d818d86fda1d280ebb06bd");
$len = strlen($cookie) - 40;
if ($len < 0) {
    show_error('The session cookie was not signed.');
}
// Check cookie authentication
$hmac = substr($cookie, $len);
$session = substr($cookie, 0, $len);
if ($hmac !== hash_hmac('sha1', $session, KEY)) {
    show_error('The session cookie data did not match what was expected.');
}
// Detect target encryption method and Decrypt session
$_mcrypt = $encryption->mcrypt_decode(base64_decode($session));
$_xor = $encryption->_xor_decode(base64_decode($session));
$method = '';
$plain = '';
if (strpos($_mcrypt, KEYWORD) !== false) {
    _print("Encryption method is mcrypt!");
    $method = 'm';
    $plain = $_mcrypt;
} else {
    if (strpos($_xor, KEYWORD) !== false) {
        _print("Encryption method is xor!");
        $method = 'x';
        $plain = $_xor;
    } else {
        show_error("something went wrong.");
    }
}