time_sleep_until

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

    time_sleep_until — Hacer que el script duerma hasta el momento especificado

    Descripción

    time_sleep_until(float $timestamp): bool

    Hace que el script duerma hasta la marca de tiempo especificada dada por timestamp.

    Parámetros

    timestamp

    La marca de tiempo en la que el script debería despertar.

    Valores devueltos

    Devuelve true en caso de éxito o false en caso de error.

    Historial de cambios

    Versión Descripción
    5.3.0 Esta función ahora está disponible en plataformas Windows.

    Errores/Excepciones

    Si la timestamp especificada está en el pasado, esta función generará un error de nivel E_WARNING.

    Ejemplos

    Ejemplo #1 Un ejemplo de time_sleep_until()

    <?php

    //devuelve false y genera una advertencia
    var_dump(time_sleep_until(time()-1));

    // puede funcionar solamente en ordenadores más rápidos, dormirá durante 0.2 segundos
    var_dump(time_sleep_until(microtime(true)+0.2));

    ?>

    Notas

    Nota: Todas las señales serán emitidas después de que despierte el script.

    Ver también

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    User Contributed Notes 3 notes

    up
    2
    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.
    up
    -2
    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 );
    }
    }
    ?>
    up
    -4
    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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