An AES encryption implementation in PHP with OpenSSL module.

OpensslAes256.php

<?php
// Set cipher method
$cipherMethod = 'AES-256-CBC';

// Set encryption key
// The key length must be 256 bits long
$key = (empty($key)) ? openssl_random_pseudo_bytes(32) : '...';

// Set initialization vector
$iv = (empty($iv)) ? openssl_random_pseudo_bytes(openssl_cipher_iv_length($cipherMethod)) : '...';

// Encryption
// openssl_encrypt uses PKCS#7 padding by default if the options parameter was set to zero
$encryptedString = openssl_encrypt($rawString, $cipherMethod, $key, 0, $iv);

// Decryption
$decryptedString = openssl_decrypt($encryptedString, $cipherMethod, $key, 0, $iv);