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

使脚本睡眠到指定的$timestamp。

参数

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

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. 

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:

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

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):

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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