请问PHP如何通过openssl实现AES-128加密算法？

class AES_128_CW {
    private $_iv = '';
    private $_secret = '';

    public function __construct($iv,$secret){
        $this->_iv = substr($iv.'0000000000000000', 0,16);//可以忽略这一步，只要你保证iv长度是16
        $this->_secret = hash('md5',$secret,true);
    }

    public function decode($secretData){
        return openssl_decrypt(urldecode($secretData),'aes-128-cbc',$this->_secret,false,$this->_iv);
    }

    public function encode($data){
        return urlencode(openssl_encrypt($data,'aes-128-cbc',$this->_secret,false,$this->_iv));
    }

}