public function makeSign($data)
{
//签名步骤一：按字典序排序参数
ksort($data);
$string = Utility::toUrlParams($data);
//签名步骤二：在string后加入KEY
$string = $string . "&key=" . $this->key;
//var_dump($string);
//签名步骤三：MD5加密
$string = md5($string);
//签名步骤四：所有字符转为大写
$result = strtoupper($string);
return $result;
}
