How to get time in PHP with nanosecond precision?

Question

Is this even possible in PHP?

If not, what is the highest precision available?

Trager

Just out of curiosity, why do you need nanosecond precision in PHP? – Outmaneuver

I'm doing something involving time synchronisation, where a program asks the remote server for it's time. Java can give the time in nanoseconds, so I thought it would be cool if I could get PHP to do that too rather than wasting the extra precision. – Trager

Answer 1

The microtime function is what you're looking for.

PHP does not supply a function that has higher precision than microseconds.

You can use the system function to get the value straight from the machine if you are running Linux:

$nanotime = system('date +%s%N');

%s is the amount of seconds, appended by %N, which is the amount of nanoseconds.

Allrud

I'm running linux, but for some reason that returns 0. Does it not work on lighttpd? – Trager

I just noticed and fixed that after googling date :P But something strange is happening, it just returns seemingly random 9 digit numbers like 519716810. It does the same when I run the command in SSH, so I don't think it's a data type issue with PHP. – Trager

If I run the command a few times in a for loop, the numbers increase from 0........ to 9........, and then back again. So it does seem like the first half of the number is missing. – Trager

Got it, I think it should be date +%s%N, because %N doesn't bother showing the seconds part. – Trager

Just out of curiosity: A system call like system need to spawn a shell and return output to PHP. Wouldn't that take a lot more than a nanosecond? If so, wouldn't it defeat the purpose of find time to nanosecond precision? Please advice. – Perineuritis

system() is writing to output, exec('date +%s%N') is more correct – Protestant

Think twice, do you really need nanoseconds, becuase there's performance drop: exec('date +%s%N'): 3.1263501644135 seconds; round(microtime(true) * 1000): 0.0062530040740967 seconds; Tested on 1000 cycles with calling this functions. – Protestant

Of interest, PHP does implement time_nanosleep() which is the only function I know that exposes nanoseconds. – Cyanotype

system('date +%s%N') makes me like a type of echo, so in a ajax result apear. – Milford

Answer 2

Now with this extension it's nanosecond timing is possible http://pecl.php.net/hrtime . Yet it is a stopwatch class implemented to suite the highest possible resolution on different platforms.

As of PHP 7.3 there's also a crossplatform hrtime() function in the core http://php.net/manual/en/function.hrtime.php.

Couch

It should be the accepted answer since hrtime()'s doc says "Returns an array of integers in the form [seconds, nanoseconds]." – Clack

Answer 3

microtime() is the highest precision using PHP's vocabulary. You can also make a system call by using Unix date and specify %N format if you need nanosecond accuracy. Unix ntp_gettime() has even higher resolution and returns jitter/wander/stability/shift/calibration data.

Melanous

Ah, I was hoping there would be something higher than that =[ – Trager