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    time_sleep_until

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

    time_sleep_until — Откладывает исполнение скрипта до заданного времени

    Описание

    time_sleep_until(float $timestamp): bool

    Откладывает исполнение скрипта до заданной временной метки, указанной в параметре timestamp.

    Список параметров

    timestamp

    Временная метка продолжения исполнения скрипта.

    Возвращаемые значения

    Возвращает true в случае успешного выполнения или false в случае возникновения ошибки.

    Ошибки

    Если указанная временная метка timestamp просрочена, то функция сгенерирует E_WARNING.

    Примеры

    Пример #1 Пример использования time_sleep_until()

    <?php

    //возвращает false и выводит предупреждение
    var_dump(time_sleep_until(time()-1));

    // может работать только на быстродействующих компьютерах, выполнение отложено до 0.2 секунд
    var_dump(time_sleep_until(microtime(true)+0.2));

    ?>

    Примечания

    Замечание: Все сигналы будут доставлены после продолжения исполнения скрипта.

    Смотрите также

    • sleep() - Задержка выполнения
    • usleep() - Задержка выполнения в микросекундах
    • time_nanosleep() - Задержка на заданное число секунд и наносекунд
    • set_time_limit() - Ограничение времени выполнения скрипта

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    User Contributed Notes 3 notes

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    0
    purdue at nc dot rr dot com
    13 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.
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    -1
    rowan dot collins at cwtdigital dot com
    12 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 );
            }
        }
    ?>
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    -2
    divinity76 at gmail dot com
    5 years ago
    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.
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