time_sleep_until()

(PHP 5 >= 5.1.0, PHP 7)

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

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 #1time_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

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 );
    }
  }
?>

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.

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.