time_sleep_until

(PHP 5 >= 5.1.0, PHP 7, PHP 8)

time_sleep_until — 使脚本睡眠到指定的时间为止。

说明

time_sleep_until ( float $timestamp ) : bool

使脚本睡眠到指定的 timestamp。

参数

timestamp: 将脚本唤醒的时间戳。

返回值

成功时返回 true，或者在失败时返回 false。

更新日志

版本	说明
5.3.0	自此，函数在Windows平台可用。

错误／异常

如果设定的 timestamp 为过去的时间，脚本将会产生一个 E_WARNING 级别的错误。

范例

Example #1 time_sleep_until() 的一个例子


<?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));

?>

注释

Note: 所有的信号会被延迟至脚本唤醒以后。

参见

sleep() - 延缓执行
usleep() - 以指定的微秒数延迟执行
time_nanosleep() - 延缓执行若干秒和纳秒
set_time_limit() - 设置脚本最大执行时间

User Contributed Notes

divinity76 at gmail dot com 28-Oct-2019 07:22


if you for some reason need a constant-time implementation of realpath(), try



<?php



function realpath_constant_time(string $path, float $target_seconds, bool &$constant_time_success = null){

    $start_time=microtime(true);

    $ret=realpath($path);

    $constant_time_success = @time_sleep_until($start_time+$target_seconds);

    return $ret;

}

?>



for example, a realtime that always uses exactly 1 millisecond (should be more than enough for SSD-based servers, perhaps rotating harddrive based servers may need something closer to 10 milliseconds, i don't know):



<?php

realpath_constant_time("/path/to/../to/file.txt",0.001,$constant_time_success);

?>



and you can use $constant_time_success to see if you needed more time (and thus failed to do realpath() in constant-time), or if you succeeded.

rowan dot collins at cwtdigital dot com 30-May-2012 10:42


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 05-May-2011 11:04


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.