phpseclib\Crypt\Rijndael::isValidEngine PHP Method

    function isValidEngine($engine)
    {
        switch ($engine) {
            case self::ENGINE_OPENSSL:
                if ($this->block_size != 16) {
                    return false;
                }
                $this->cipher_name_openssl_ecb = 'aes-' . ($this->key_length << 3) . '-ecb';
                $this->cipher_name_openssl = 'aes-' . ($this->key_length << 3) . '-' . $this->_openssl_translate_mode();
                break;
            case self::ENGINE_MCRYPT:
                $this->cipher_name_mcrypt = 'rijndael-' . ($this->block_size << 3);
                if ($this->key_length % 8) {
                    // is it a 160/224-bit key?
                    // mcrypt is not usable for them, only for 128/192/256-bit keys
                    return false;
                }
        }
        return parent::isValidEngine($engine);
    }