$string = "Mary had a little lamb.";
$key = "My Secret Key";
 
// Encryption Algorithm
$alg = MCRYPT_RIJNDAEL_256;
// Create the initialization vector for increased security.
$iv = mcrypt_create_iv(mcrypt_get_iv_size($alg, MCRYPT_MODE_ECB), MCRYPT_RAND);
 
// Output the original string
PRINT "The original string is: $string <p>";
 
// Encrypt $string
$encrypted_string = mcrypt_encrypt($alg, $key, $string, MCRYPT_MODE_CBC, $iv);
 
// Convert to hexadecimal and output to browser
 
PRINT "The encrypted string is: ".BIN2HEX($encrypted_string)."<p>";
$decrypted_string = mcrypt_decrypt($alg, $key, $encrypted_string, MCRYPT_MODE_CBC, $iv);
 
PRINT "The decrypted string is: $decrypted_string";