## 20位隨機數
```
/**
* 生成20位隨機數
* @param [type] $type [類型，1：訂單號，2隨機數]
* @param integer $num [數量]
* @return [type] [字符串]
*/
function randomCode(){
list($usec, $sec) = explode(" ", microtime());
// 0.78994600 1595664806
$data = explode(".",$usec);
$sm = $sec.substr($data[1],0,7);
$guid = $sm.mt_rand(100,999);
return $guid;
}
```
