How to use time to name files in PHP to prevent the system from automatically naming duplicates?

If it is only accurate to seconds, you can use the time() function result.

In order to avoid duplication at all, even if multiple files are uploaded within one second, a 3-digit random number should be added. The code is as follows:

$fname=time(). rand(100,999);

Or:

$fname=date('YmdHis').rand(100,999);