Clase para encriptacion con el metodo AES128

<?php
/**
 * Clase para encriptacion con el metodo AES128.
 *
 * @author Roberto I Ramirez N <robertoiran [at] gmail.com>
 */
final class CipherAES
{
    private $_key = NULL;

    private $_iv = NULL;

    public function __construct($key = NULL, $iv = NULL, $bin = TRUE)
    {
        $this->setKey($key, $bin);
        $this->setIV($iv, $bin);
    }

    public function setKey($key = NULL, $bin = TRUE)
    {
        $this->_key = $bin ? hex2bin($key) : $key;
    }

    public function setIV($iv = NULL, $bin = TRUE)
    {
        $this->_iv = $bin ? hex2bin($iv) : $iv;
    }

    public function encrypt($string = NULL, $output_hex = TRUE)
    {
        $enc = NULL;

        $size = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
        $td = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, '');
        if(mcrypt_generic_init($td, $this->_key, $this->_iv) != -1)
        {
            $clearPadd = $this->_pkcs5_pad($string,$size);
            $enc = mcrypt_generic($td, $clearPadd);
            mcrypt_generic_deinit($td);
        }
        mcrypt_module_close($td);
        return $output_hex ? bin2hex($enc) : $enc;
    }

    public function decrypt($string = NULL, $input_hex = TRUE)
    {
        $dec = NULL;
        $string = $input_hex ? hex2bin($string) : $string;

        $size = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
        $td = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_CBC, '');
        if(mcrypt_generic_init($td, $this->_key, $this->_iv) != -1)
        {
            $dec = mdecrypt_generic($td, $string);
            $decWOPadding = $this->_pkcs5_unpad($dec);
            mcrypt_generic_deinit($td);
        }
        mcrypt_module_close($td);
        return $decWOPadding;
    }

    private function _pkcs5_pad($text, $blocksize)
    {
        $pad = $blocksize - (strlen($text) % $blocksize);
        return $text . str_repeat(chr($pad), $pad);
    }

    private function _pkcs5_unpad($text)
    {
        $pad = ord($text{strlen($text)-1});
        if ($pad > strlen($text)) return false;
        if (strspn($text, chr($pad), strlen($text) - $pad) != $pad) return false;
        return substr($text, 0, -1 * $pad);
    }
}

if(!function_exists('hex2bin'))
{
    function hex2bin($str)
    {
        return pack('H*',$str);
    }
}

/**
 * Ejemplo de uso
 */
$size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC);
$_iv = mcrypt_create_iv($size, MCRYPT_DEV_RANDOM);
$_key = '74e6ac8eec9f8e9d2401f318cbd361551e3f721a4f4f9aab313bdfb9f61af932';

$CipherAES = new CipherAES($_key, bin2hex($_iv));
$string = 'Hola Mundo!';
$strEnc = $CipherAES->encrypt($string);
$strDec = $CipherAES->decrypt($strEnc);

echo 'Cadena original: ', $string, '<br />';
echo 'Cadena encriptada: ', $strEnc, '<br />';
echo 'Cadena desencriptada: ', $strDec;