怎样生成一个不重复的随机数-PHP Tutorial-php.cn

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怎样生成一个不重复的随机数

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Jun 06, 2016 pm 08:41 PM

phprandom number

至少有下列要求

是散列而且随机的，至少不会被猜到序列规则
是永不重复的，如果生成一次去验证是否存在，那效率是不是太低？

回复内容：

至少有下列要求

是散列而且随机的，至少不会被猜到序列规则
是永不重复的，如果生成一次去验证是否存在，那效率是不是太低？

推荐参考mongodb的ObjectId生成机制。 ObjectId一共12个字节

4字节的时间戳，放在第一部分可以使ObjectId "大致"遵循时间顺序，保证不同秒数生成的ID一定不重复
3字节的机器ID，默认通过机器的各种基础信息hash而来，保证同一秒不同机器生成的ID一定不重复
2字节的进程号，保证同一秒同一机器不同进程生成的ID一定不重复
3字节的自增，在同一秒内自增，保证同一秒同一机器同一进程内生成的16777216个 ID一定不重复

可不可以使用UUID，如果想换成数字的话，那就做下转换。
可能数字会比较大，要自己定义下规则，缩小。

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