PHP Class - OpenSSL Encryption

<?php
    /* ========================================
    Class for encrypting and decrypting data
    using the OpenSSL and MCRYPT libraries

    Requires PHP 5.4+ and the OpenSSL and
    MCRYPT libraries be installed.

    @author: rbrotherton@gmail.com
    @license: Unlicensed
   ======================================== */

    class OpenSSL {

        protected $cipher_mcrypt  = MCRYPT_RIJNDAEL_128;
        protected $cipher_openssl = 'aes-256-cbc';

        // Constructor
        public function __construct(){

        }

        // How to behave when treated like a string
        public function __toString(){
            return "OpenSSL/MCRYPT encryption object.";
        }

        public function encrypt($data, $key){

            $vector_size = mcrypt_get_iv_size($this->cipher_mcrypt, MCRYPT_MODE_CBC);
            $vector      = mcrypt_create_iv($vector_size, MCRYPT_DEV_URANDOM);
            $encrypted   = openssl_encrypt($data, $this->cipher_openssl, $key, 0, $vector);

            // Pass the initialization vector along with our data string so we can decode later
            return $vector . $encrypted;

        }

        public function decrypt($data, $key){

            $vector_size = mcrypt_get_iv_size($this->cipher_mcrypt, MCRYPT_MODE_CBC);
            $vector      = substr($data, 0, $vector_size);
            $data        = substr($data, $vector_size);
            return openssl_decrypt($data,$this->cipher_openssl, $key, 0, $vector);

        }

    }


?>