Difference among sleep() and usleep() in PHP

Question

Can any body explain me what is the difference among sleep() and usleep() in PHP.

I have directed to use following scripts to do chat application for long pulling but in this script I am getting same effect using usleep(25000); or without usleep(25000);

page1.php

<script src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js" 
       type="text/javascript"></script>

<script>
var lpOnComplete = function(response) {
    console.log(response);
    // do more processing
    lpStart();
};

var lpStart = function() {
    $.post('page2.php', {}, lpOnComplete, 'json');
};

$(document).ready(lpStart);
</script>

page2.php

<?php
$time = time();
while((time() - $time) < 30) {
    // query memcache, database, etc. for new data
    $data = getLatest();

    // if we have new data return it
    if(!empty($data)) {
        echo json_encode($data);
        break;
    }

    usleep(25000);
}

function getLatest() {
    sleep(2);
    return "Test Data"; 
}
?>

sleep() takes a number of seconds as its parameter and usleep() takes a number of microseconds - millionths of a second as its parameter. — Ranjitsinh, Oct 24 '13 at 05:30
http://wordpressapi.com/how-to-use-sleep-usleep-function-in-php/ — Dipesh Parmar, Oct 24 '13 at 05:30

score 43 · Accepted Answer · answered Oct 24 '13 at 05:30

43

The argument to sleep is seconds, the argument to usleep is microseconds. Other than that, I think they're identical.

sleep($n) == usleep($n * 1000000)

usleep(25000) only sleeps for 0.025 seconds.

answered Oct 24 '13 at 05:30

Barmar

741,623
53
500
612

4

Another important difference is that usleep uses CPU cycles, sleep does not. – Ellert van Koperen Feb 08 '19 at 12:24
@EllertvanKoperen Wouldn't that depend on whether the OS provides a built-in way to do sub-second sleeps? – Barmar Feb 08 '19 at 15:48
That, and wether you use some big chunks or many small chunks of sleepytime. – Ellert van Koperen Feb 08 '19 at 23:01
If there's a performance difference, it's almost certainly negligible and not worth updating the answer over. – Barmar Feb 09 '19 at 02:16

score 6 · Answer 2 · edited Oct 12 '17 at 15:39

6

sleep() allows your code to sleep in seconds.

sleep(5); // sleeps for 5 seconds

usleep() allows your code with respect to microseconds.

usleep(2500000); // sleeps for 2.5 seconds

edited Oct 12 '17 at 15:39

COil

7,201
2
50
98

answered Oct 24 '13 at 06:29

Ashwin

993
1
16
41

score 2 · Answer 3 · edited Oct 24 '13 at 06:04

2

usleep() is used to delay execution in "microseconds" while sleep() is used to delay execution in seconds. So usleep(25000) is 0.025 seconds.

Is there any difference between the two?

edited Oct 24 '13 at 06:04

Zo Has

12,599
22
87
149

answered Oct 24 '13 at 05:37

shahpranaf

121
1
5

score 2 · Answer 4 · answered Sep 18 '17 at 10:35

2

One other difference is sleep returns 0 on success, false on error. usleep doesn't return anything.

answered Sep 18 '17 at 10:35

qualia

41
2

1

you can just mention it in a comment in the accepted answer – Greg Sep 18 '17 at 10:54
1

@Grzegorz Actually, I can't because I need 50 rep to comment. – qualia Feb 18 '20 at 11:29

score 1 · Answer 5 · answered Jun 11 '19 at 11:59

1

Simply

usleep uses CPU Cycles while sleep does not.

sleep takes seconds as argument

while usleep takes microseconds as argument

answered Jun 11 '19 at 11:59

Dev Matee

5,525
2
27
33

Difference among sleep() and usleep() in PHP

5 Answers5

Linked

Related