What to use ? time() function or $_SERVER['REQUEST_TIME'] ? Which is better?

Question

Which one among these two time functions is better?

I have a form on my website which is submitted by thousands of users every microsecond or less , thus , thousands of requests at the same time on my server.

So I want to use the one which does not uses any sleep while execution. Also , how unique is $_SERVER['REQUEST_TIME'] and time()? Do both change every microsecond?

Will $_SERVER['REQUEST_TIME'] change every time I submit the form? Like , the time() function will change at every time difference.

I need to give a unique url to the user for verification in which am appending the unique result generated from any one of the two? Also, using microtime() would make PHP sleep? isn't it?

Answer 1

It depends.

$_SERVER['REQUEST_TIME'] corresponds to the time when the request has started, the web server provides this data.

time() actually runs a syscall in order to check the time when this line is called.

You need to be more specific on what you want to do so we can give you complete answers.