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Last updated: Fri, 12 Mar 2010

sleep

(PHP 4, PHP 5)

sleep — Delay execution

Description

int sleep ( int $seconds )

Delays the program execution for the given number of seconds .

Parameters

seconds: Halt time in seconds.

Return Values

Returns zero on success, or FALSE on errors. If the call was interrupted by a signal, sleep() returns the number of seconds left to sleep.

Errors/Exceptions

If the specified number of seconds is negative, this function will generate a E_WARNING.

Examples

Example #1 sleep() example


<?php

// current time
echo date('h:i:s') . "\n";

// sleep for 10 seconds
sleep(10);

// wake up !
echo date('h:i:s') . "\n";

?>

This example will output (after 10 seconds)

05:31:23
05:31:33


Notice that sleep() delays execution for the current session, not just the script. Consider the following sample, where two computers invoke the same script from a browser, which doesn't do anything but sleep.





PC 1 [started 14:00:00]: script.php?sleep=10 // Will stop after 10 secs


PC 1 [started 14:00:03]: script.php?sleep=0 // Will stop after 7 secs





PC 2 [started 14:00:05]: script.php?sleep=0 // Will stop immediately





http://php.net/session_write_close may be used to address this problem.

mohd at Bahrain dot Bz
16-Dec-2009 09:12


I hope this code will help somebody to solve the problem of not being able to flush or output the buffer to the browser (I use IE7).

It may work for you with just [ echo str_repeat(".", 4096); ] and without even using ob_... and flush.



<?php

ob_start();



ob_implicit_flush(true);

//[ OR ] echo "..."; ob_flush(); flush();



set_time_limit(0);



function sleep_echo($secs) {

    $secs = (int) $secs;

    $buffer = str_repeat(".", 4096);

    //echo $buffer."\r\n<br />\r\n";

    for ($i=0; $i<$secs; $i++) {

        echo date("H:i:s", time())." (".($i+1).")"."\r\n<br />\r\n".$buffer."\r\n<br />\r\n";

        ob_flush();

        flush();

        sleep(1);

        //usleep(1000000);

    }

}



sleep_echo(30);



ob_end_flush();

?>

f dot schima at ccgmbh dot de
10-Nov-2009 02:48


Remember that sleep() means "Let PHP time to do some other stuff".

That means that sleep() can be interrupted by signals. That is important if you work with pcntl_signal() and friends.

Anonymous
08-Feb-2009 08:32


This will allow you to use negative values or valuer below 1 second.





<?php slaap(0.5); ?>





<?php


function slaap($seconds)


{


    $seconds = abs($seconds);


    if ($seconds < 1):


       usleep($seconds*1000000);


    else:


       sleep($seconds);


    endif;    


}


?>

webseos at gmail dot com
27-Aug-2008 04:29


This is a critical thing to use time delay function as sleep() Because a beginner can find that this is not working and he/she will see that all output appearing at a time.



A good way to implement this is by using the function -  ob_implicit_flush() then you don't need to use flush() function explicitly.



A sample code :

<?php

ob_implicit_flush(true);

for($i=0;$i<5;$i++)

{

$dis=<<<DIS

<div style="width:200px; background-color:lime;border:1px; text-align:center;text-decoration:blink;">

$i

</div>

DIS;

echo $dis;



sleep(5);

//flush();

}

marpetr at gmail dot com
18-Mar-2008 07:41


Very useful to prevent password brute forcing! Simply add few seconds timeout to login script and the probability to guess the password decreases a lot!

linus at flowingcreativity dot net
08-Jul-2005 03:07


This may seem obvious, but I thought I would save someone from something that just confused me: you cannot use sleep() to sleep for fractions of a second. This:



<?php sleep(0.25) ?>



will not work as expected. The 0.25 is cast to an integer, so this is equivalent to sleep(0). To sleep for a quarter of a second, use:



<?php usleep(250000) ?>

MPHH
05-Jul-2003 07:33


Note: The set_time_limit() function and the configuration directive max_execution_time only affect the execution time of the script itself. Any time spent on activity that happens outside the execution of the script such as system calls using system(), the sleep() function, database queries, etc. is not included when determining the maximum time that the script has been running.

hartmut at six dot de
25-Aug-2000 01:38


it is a bad idea to use sleep() for delayed output effects as





1) you have to flush() output before you sleep





2) depending on your setup flush() will not work all the way to the browser as the web server might apply buffering of its own or the browser might not render output it thinks not to be complete





netscape for example will only display complete lines and will not show table parts until the </table> tag arrived





so use sleep if you have to wait  for events and don't want to burn  to much cycles, but don't use it for silly delayed output effects!

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