function refund_decrypt($str, $key)
{
    $key = md5($key);
    $str = base64_decode($str);
    $str = openssl_decrypt($str,'aes-256-ecb',$key,OPENSSL_RAW_DATA);
    $len = strlen($str);
    $pad = ord($str[$len - 1]);
    return substr($str, 0, strlen($str) - $pad);
}