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sleep

(PHP 4, PHP 5, PHP 7, PHP 8)

sleepDelay execution

Description

sleep(int $seconds): int

Delays the program execution for the given number of seconds.

Note:

In order to delay program execution for a fraction of a second, use usleep() as the sleep() function expects an int. For example, sleep(0.25) will pause program execution for 0 seconds.

Parameters

seconds

Halt time in seconds (must be greater than or equal to 0).

Return Values

Returns zero on success.

If the call was interrupted by a signal, sleep() returns a non-zero value. On Windows, this value will always be 192 (the value of the WAIT_IO_COMPLETION constant within the Windows API). On other platforms, the return value will be the number of seconds left to sleep.

Errors/Exceptions

If the specified number of seconds is negative, this function will throw a ValueError.

Changelog

Version Description
8.0.0 The function throws a ValueError on negative seconds; previously, an E_WARNING was raised instead, and the function returned false.

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

See Also

add a note

User Contributed Notes 12 notes

up
50
ash b
10 years ago
re: "mitigating the chances of a full bruit force attack by a limit of 30 lookups a minute."

Not really - the attacker could do 100 requests. Each request might take 2 seconds but it doesn't stop the number of requests done. You need to stop processing more than one request every 2 seconds rather than delay it by 2 seconds on each execution.
up
40
MPHH
21 years ago
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.
up
3
John
10 months ago
To avoid using usleep function that is not working on every operating system, below a function that should have the same behavior :

function wait(int $millisecond = 0) {
if (0 !== $millisecond) {
$seconds = (int) ($millisecond / 1000);
$nanoSeconds = ($millisecond % 1000) * 1000000;
time_nanosleep($seconds, $nanoSeconds);
}
}
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33
barlow at fhtsolutions dot com
13 years ago
You should put sleep into both the pass and fail branches, since an attacker can check whether the response is slow and use that as an indicator - cutting down the delay time. But a delay in both branches eliminates this possibility.
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22
Diego Andrade
8 years ago
Maybe obvious, but this my function to delay script execution using decimals for seconds (to mimic sleep(1.5) for example):

<?php
/**
* Delays execution of the script by the given time.
* @param mixed $time Time to pause script execution. Can be expressed
* as an integer or a decimal.
* @example msleep(1.5); // delay for 1.5 seconds
* @example msleep(.1); // delay for 100 milliseconds
*/
function msleep($time)
{
usleep($time * 1000000);
}
?>
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13
Anonymous
6 years ago
Diego Andrade's msleep function is not compatible with php7's `strict_types`, cast the usleep parameter to int, and it will be,
usleep((int)($time * 1000000));
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9
hartmut at six dot de
24 years ago
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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2
Anonymous
10 years ago
If you are having issues with sleep() and usleep() not responding as you feel they should, take a look at session_write_close()

as noted by anonymous on comments;
"If the ajax function doesn't do session_write_close(), then your outer page will appear to hang, and opening other pages in new tabs will also stall."
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0
ealexs at gmail dot com
2 years ago
From my testing calling sleep(0); will do a `thread spin`.
It would be nice if this was to be put explicitly in the documentation as it is useful. You can do the minimum wait without overloading the CPU thread.
up
0
Anonymous
3 years ago
I wrote a simple method for sleeping with a float, which also allows you to do milliseconds (via fractional seconds).

<?php
function sleepFloatSecs($secs) {
$intSecs = intval($secs);
$microSecs = ($secs - $intSecs) * 1000000;

if(
$intSecs > 0) {
sleep($intSecs);
}
if(
$microSecs > 0) {
usleep($microSecs);
}
}
?>

And testing on my machine it works perfectly:

<?php
$x
= [0.100,0.250,0.5,1.0,1.5,2.0,2.5];

foreach(
$x as $secs) {
$t = microtime(true);
sleepFloatSecs($secs);
$t = microtime(true) - $t;
echo
"$secs \t => \t $t\n";
}
?>

Output:

<?php
0.1
=> 0.10017800331116
0.25
=> 0.25016593933105
0.5
=> 0.50015211105347
1
=> 1.0001430511475
1.5
=> 1.5003218650818
2
=> 2.000167131424
2.5
=> 2.5002470016479
?>
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-5
manu7772 at gmail dot com
3 years ago
Sleep method with parameter in milliseconds :

public static function ms_sleep($milliseconds = 0) {
if($milliseconds > 0) {
$test = $milliseconds / 1000;
$seconds = floor($test);
$micro = round(($test - $seconds) * 1000000);
if($seconds > 0) sleep($seconds);
if($micro > 0) usleep($micro);
}
}
up
-3
smcbride at msn dot com
3 years ago
An example of using sleep to run a set of functions at different intervals. This is not a replacement for multi-threading, but it could help someone that wants to do something cheap. You don't have to use eval(). It is just used as an example. This is different than running a standard 1 second sleep loop, due to sleeping longer does not consume as much CPU.

<?php

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

// Some example functions
function function_a() { echo 'function_a called @ ' . date('h:i:s') . PHP_EOL; }
function
function_b() { echo 'function_b called @ ' . date('h:i:s') . PHP_EOL; }
function
function_c() { echo 'function_c called @ ' . date('h:i:s') . PHP_EOL; }

// Add some timers (in seconds) with function calls
$sleeptimers = array();
$sleeptimers['5'][0]['func'] = 'function_a();';
$sleeptimers['10'][0]['func'] = 'function_b();';
$sleeptimers['15'][0]['func'] = 'function_c();';

// Process the timers
while(true) {
$currenttime = time();
reset($sleeptimers);
$mintime = key($sleeptimers);
foreach(
$sleeptimers as $SleepTime => $Jobs) {
foreach(
$Jobs as $JobIndex => $JobDetail) {
if(!isset(
$JobDetail['lastrun'])) {
$sleeptimers[$SleepTime][$JobIndex]['lastrun'] = time();
if(
$SleepTime < $mintime) $mintime = $SleepTime;
} elseif((
$currenttime - $JobDetail['lastrun']) >= $SleepTime) {
eval(
$JobDetail['func']);
$lastrun = time();
$sleeptimers[$SleepTime][$JobIndex]['lastrun'] = $lastrun;
$mysleeptime = $SleepTime - ($currenttime - $lastrun);
if(
$mysleeptime < 0) $mysleeptime = 0;
if((
$currenttime - $JobDetail['lastrun']) < $mintime) $mintime = $mysleeptime; // account for length of time function runs
echo 'Sleep time for function ' . $JobDetail['func'] . ' = ' . $mysleeptime . PHP_EOL;
}
}
}
echo
'Sleeping for ' . $mintime . ' seconds' . PHP_EOL;
sleep($mintime);
}

?>
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