订单编号有关问题求解
订单编号问题求解？
$orderid=GB_.substr(date('YmdHis')).mt_rand(0,999999);
这样是对的吗？
为什么得到的 GB_465505 是这样的，中间的时期没有呢？这样这个订单编号相同机率会有多大？
------解决方案--------------------
随机数当然概率是一样大 不过也有重复的可能
------解决方案--------------------
GB_.substr(date('YmdHis')).mt_rand(0,999999);
substr($string, $start, $length);
这个方法要三个参数，第一个是字符串，也就是你的时间，第二个是截取开始位置，第三个是截取长度
------解决方案--------------------
$orderid = 'GB_' . date('YmdHis') . mt_rand(0,999999);
虽然使用随机数出现冲突的概率不大（对你是百万分之一）
但他不连续，不便于管理。也不能防止伪造
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