AES encryption/decryption in PHP

aes_enc_dec.php

<?php
// DEFINE our cipher
define('AES_256_CBC', 'aes-256-cbc');

// Generate a 256-bit encryption key
// This should be stored somewhere instead of recreating it each time
$encryption_key = openssl_random_pseudo_bytes(32);

// Generate an initialization vector
// This *MUST* be available for decryption as well
$iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length(AES_256_CBC));

// Create some data to encrypt
$data = "Encrypt me, please!";
echo "Before encryption: $data\n";

// Encrypt $data using aes-256-cbc cipher with the given encryption key and 
// our initialization vector. The 0 gives us the default options, but can
// be changed to OPENSSL_RAW_DATA or OPENSSL_ZERO_PADDING
$encrypted = openssl_encrypt($data, AES_256_CBC, $encryption_key, 0, $iv);
echo "Encrypted: $encrypted\n";

// If we lose the $iv variable, we can't decrypt this, so append it to the 
// encrypted data with a separator that we know won't exist in base64-encoded 
// data
$encrypted = $encrypted . ':' . $iv;

// To decrypt, separate the encrypted data from the initialization vector ($iv)
$parts = explode(':', $encrypted);
// $parts[0] = encrypted data
// $parts[1] = initialization vector

$decrypted = openssl_decrypt($parts[0], AES_256_CBC, $encryption_key, 0, $parts[1]);
echo "Decrypted: $decrypted\n";
?>