PHP: usleep - Manual

Description

void usleep ( int micro_seconds )

The usleep() function delays program execution for the given number of micro_seconds. A microsecond is one millionth of a second.

Example 1. usleep() example

<?php // Current time echo date('h:i:s') . "\n"; // wait for 2 secondes usleep(2000000); // back! echo date('h:i:s') . "\n"; ?>
This script will output :
11:13:28 11:13:30

Note: This function did not work on Windows systems until PHP 5.0.0

See also sleep() and set_time_limit().

User Contributed Notes
usleep

t0russ at gmail dot com
03-May-2005 10:06


solution to the warning posted by Bertie:

$f=@fsockopen("tcp://localhost",$UNUSED_PORT,$errno,$errstr,$delay);

@fclose($f);

brian dot hollenbeck at gmail dot com
25-Mar-2005 06:28


Just a tip for the folks at home: is you use multiple rand() functions in your code, be sure to put a randomized usleep() in between the rand() codelines, or else your "random" seeds won't be so random on a fast server.



Example:



$string = rand(0, 100);

$string = rand(0, 200);



Instead:



$string = rand(0, 100);

usleep(rand(1000, 10000));

$string1 = rand(0, 100);

Bertie
28-Nov-2003 01:47


A word of warning about the microdelay() code posted that uses the fsockopen - if you use this is a loop that delays for small periods you will very quickly run out of sockets/socket buffer space. And then your network connections go very strange......

grail dot ink at unix dot net
29-Aug-2003 04:06


We have developed an alternative to usleep that should work on any platform and it doesn't eat up any CPU cycles. It's been tested on Windows 2000 w/ Apache. Other platforms should work fine.



function microdelay($delay) {

$UNUSED_PORT=31238; //make sure this port isn't being used on your server

@fsockopen("tcp://localhost",$UNUSED_PORT,$errno,$errstr,$delay);

}



It times out after a specified time in seconds. It uses a double as argument so you can specify decimal arguments.



microdelay(.5); //500ms

microdelay(.25); //250ms

microdelay(2.25); //2250ms



Our small contribution to this great language!



http://www.xencoders.com

jadd0r at mail dot com
08-Apr-2003 12:59


You could do neat things with this like for unix:



<?php

$y=1000000;

for ($x=1; $x<50; $x++) {

echo chr(7);

usleep($y*(pow(0.9,$x)+0.2));

}

?>



then execute

`php -q script.php > /dev/console`



will result in a bombtimer (chr(7) is beep character) :]

busby at edoceo dot com
17-Jan-2003 06:04


Should be noted that functions that loop really fast to create a delay also consume 100% CPU while doing the loop.  Try creating a dummy loop that goes 100000 times, watch it choke your machine.  If you really need usleep() don't use windows.

dsc at c2i dot net
14-Mar-2002 11:55


The usleep() for Windows above doesn't take into account that the value of $stop can be lower than $start. It also contains unnecessary casts and $temp variable. Here is a better function:



function usleepWindows($usec)

{

    $start = gettimeofday();



    do

    {

        $stop = gettimeofday();

        $timePassed = 1000000 * ($stop['sec'] - $start['sec'])

            + $stop['usec'] - $start['usec'];

    }

    while ($timePassed < $usec);

}

dave at techweavers dot net
28-Dec-2000 09:29


To monitor a scripts CPU ussage and avoid any nasty CPU gobbling loops you can use this function (will not work with windows or safe mode) I know it works on FreeBSD:


function phpmon($max)


 {


 $cmd = `ps -Unobody -r -o%cpu`;


 $lines = explode("\n", $cmd);


 $usage = substr($lines[1], 0, strpos($lines[1], "."));


 $sleeprate = 500;


 while ($usage >= $max)


  {


  $cmd = `ps -Unobody -r -o%cpu`;


  $lines = explode("\n", $cmd);


  $usage = substr($lines[1], 0, strpos($lines[1], "."));


  usleep($sleeprate);


  }


 }





phpmon($MAX); 





where $MAX is the maximum CPU you want the process to consume. e-mail me with any improvements/suggestions.





I have noticed that this consumes a lot of system CPU (at least in my limited testing) possibly from all of the system calls or the huge mathematical functions I used to test the effectiveness of the script.

beidson at calpoly dot edu
14-Sep-2000 01:18


Since USLEEP doesn't work under windows, you need to come up with your own fix.  This little function will do the trick.





function wait($usecs){


  $temp=gettimeofday();


  $start=(int)$temp["usec"];


  while(1){


    $temp=gettimeofday();


    $stop=(int)$temp["usec"];


    if ($stop-$start >= $usecs) break;


  }


}





The smallest amount of time it seems to work with is around 200usecs, but if you wait() anything higher than 200usecs it's pretty close.