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。

User Contributed Notes

kuba at valentine dot dev 24-Oct-2020 08:25


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;

Gao,Shengwei 19-Apr-2018 05:12


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);

}