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;
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。
add a note
User Contributed Notes 2 notes
kuba at valentine dot dev ¶
3 years ago
Gao,Shengwei ¶
6 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);
}
