time_sleep_until

(PHP 5 >= 5.1.0, PHP 7)

time_sleep_until — Make the script sleep until the specified time

Description

bool time_sleep_until ( float $timestamp )

Makes the script sleep until the specified timestamp.

Parameters

timestamp: The timestamp when the script should wake.

Return Values

Returns TRUE on success or FALSE on failure.

Changelog

Version	Description
5.3.0	This function is now available on Windows platforms.

Errors/Exceptions

If the specified timestamp is in the past, this function will generate a E_WARNING.

Examples

Example #1 A time_sleep_until() example


<?php

//returns false and generates a warning
var_dump(time_sleep_until(time()-1));

// may only work on faster computers, will sleep up to 0.2 seconds
var_dump(time_sleep_until(microtime(true)+0.2));

?>

Notes

Note: All signals will be delivered after the script wakes up.

User Contributed Notes

rowan dot collins at cwtdigital dot com

3 years ago


Not realising that this function existed, I wrote something similar, but it has the additional facility to specify a minimum pause even if the target time has already been reached, for instance in a processor-intensive loop.

It's in seconds rather than microseconds (it's intended for heavy-duty CLI scripts), but that could easily be changed by using microtime(true) and usleep if greater granularity was required.

<?php
    /**
     * Pause processing until the specified time, to avoid hammering a DB or service
     *
     * @param int $target_time Timestamp
     * @param int $min_sleep Always sleep for a minimum number of seconds,
     *    even if the target timestamp has already passed.
     *     Default 0, meaning only sleep until the target timestamp is reached.
     *
     * @example <code>
         while ( ! $finished )
         {
             $minimum_start_of_next_loop = time() + $min_secs_per_loop;
             
             # DO STUFF THAT MAY OR MAY NOT TAKE VERY LONG
             
             sleep_until( $minimum_start_of_next_loop, $min_pause_between_loops );
         }
     </code>
     */
    function sleep_until($target_time, $min_sleep = 0)
    {
        $time_now = time();
        
        $time_to_target = $target_time - $time_now;
        
        // If we've already reached the target time, that's fine
        if ( $time_to_target <= $min_sleep )
        {
            // If required, sleep for a bit anyway
            sleep( $min_sleep );
        }
        else
        {
            // Sleep for the number of seconds until the target time
            sleep( $time_to_target );
        }
    }
?>

purdue at nc dot rr dot com

4 years ago


At least on my Windows machine, the time_sleep_until function appears to calculate the number of microseconds between now and the sleep-until timestamp, and it appears to use unsigned 32-bit math in this calculation.  This roundoff leads to a maximum sleep time of just under 4295 seconds (1 hour, 11 minutes, 35 seconds).  To get longer sleep times, while still using time_sleep_until to minimize processor overhead, the following loop may be some help to you:

<?php

$sleepuntil = strtotime("tuesday 3pm");

while (time() < $sleepuntil)
   time_sleep_until($sleepuntil);

// proceed with dated processing

?>

Of course, one could use something like "cron" instead, to avoid the script doing the extended sleep.  Also note that time_nanosleep appears to do similar math, but it is somewhat more intuitive that the seconds parameter has an upper limit on what it can be.  Still, both functions might report a warning when waking up prematurely due to roundoff.

roberto at spadim dot com dot br

9 years ago


better implementation 
<?php
if (!function_exists('time_sleep_until')) {
   function time_sleep_until($future) {
       if ($future < time()) {
           trigger_error("Time in past", E_USER_WARNING);
           return false;
       }

       usleep(($future - microtime(1))*1000000);
       return true;
   }
}
?>