pcntl_alarm
(PHP 4 >= 4.3.0, PHP 5, PHP 7, PHP 8)
pcntl_alarm — 为进程设置一个alarm闹钟信号
说明
pcntl_alarm(int
$seconds
): int
创建一个计时器,在指定的秒数后向进程发送一个SIGALRM
信号。每次对
pcntl_alarm()的调用都会取消之前设置的alarm信号。
参数
-
seconds
-
等待的秒数。如果
seconds
设置为0,将不会创建alarm信号。
返回值
返回上次alarm调度(离alarm信号发送)剩余的秒数,或者之前没有alarm调度(译注:或者之前调度已完成)
时返回0
。
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User Contributed Notes 3 notes
kuba at valentine dot dev ¶
1 year ago
This is that universal timeout functionality you dreamed about and always wanted to have and guess what - it's as reliable as it gets, it's basically bulletproof. It can interrupt absolutely anything you throw at it and more, you name it - socket_connect(), socket_read(), fread(), infinite while() loops, sleep(), semaphores - seriously, any blocking operation. You can specify your own handler and just get over anything that normally would make your code unresponsive.
<?php
/**
* Because we shouldn't handle asynchronous
* events in synchronous manner.
*/
pcntl_async_signals(TRUE);
/**
* Some flag we can change to know for sure
* that our operation timed out.
*/
$timed_out = FALSE;
/**
* Register SIGALRM signal handler to avoid
* getting our process killed when signal arrives.
*/
pcntl_signal(SIGALRM, function($signal) use (&$timed_out) {
$timed_out = TRUE;
});
/**
* Now we set our timeout for 2 seconds, but it's not set in stone
* we can call pcntl_alarm() anytime to extend or to turn if off.
*/
pcntl_alarm(2);
/**
* Here we do something with unpredictable outcome that could
* possibly block our program for a very long time.
* I like sockets as an example, but it can be anything.
*/
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
$connection = socket_connect($socket, 'irc.ircnet.com', 6667);
/**
* If our blocking operation didn't timed out then
* timer is still ticking, we should turn it off ASAP.
*/
$timed_out || pcntl_alarm(0);
/**
* And now we do whatever we want to do.
*/
$status = $connection ? 'Connected.' : ($timed_out ? 'Timed out.' : socket_strerror(socket_last_error($socket)));
echo 'STATUS: '. $status . PHP_EOL;
molsavsky1 at gmail dot com ¶
6 months ago
Beware that pcntl_signal will interrupt (u)sleep calls which will not be resumed once the handler is completed.
It's a documented behaviour (https://www.php.net/manual/en/function.sleep.php) although it may look like a bug when encountered for the first time.
From the docs:
"If the call was interrupted by a signal, sleep() returns a non-zero value. On Windows, this value will always be 192 (the value of the WAIT_IO_COMPLETION constant within the Windows API). On other platforms, the return value will be the number of seconds left to sleep."
```
<?php
$interval = 1;
pcntl_async_signals(true);
pcntl_signal(SIGALRM, function () use ($interval): void {
echo 'SIGALRM called' . PHP_EOL;
pcntl_alarm($interval);
});
pcntl_alarm($interval);
echo 'Sleep (will be interrupted) started' . PHP_EOL;
sleep(100000000000);
echo 'Sleep ended soon due to interrupt' . PHP_EOL;
$sleepTimeout = 10;
echo "Proper sleep for {$sleepTimeout} seconds" . PHP_EOL;
$startedAt = time();
while ($sleepTimeout > 0 && ($sleepTimeout = sleep($sleepTimeout)) !== true) {
echo "Sleep interrupted, {$sleepTimeout} seconds remaining" . PHP_EOL;
}
$elapsed = time() - $startedAt;
echo "Sleep finished after {$elapsed} seconds" . PHP_EOL;
```
Gao,Shengwei ¶
4 years ago
Use pcntl_signal_dispatch() to catch the signal, don't use declare(ticks=1) because it is ineffcient
<?php
pcntl_signal(SIGALRM, function () {
echo 'Received an alarm signal !' . PHP_EOL;
}, false);
pcntl_alarm(5);
while (true) {
pcntl_signal_dispatch();
sleep(1);
}