本文将简述如何快速了解 PHP 的多进程编程,并提供实验脚本。
函数
为快速入门,本文只使用多进程的两个函数:pcntl_fork 和 pcntl_waitpid
多进程开发最重要的函数 pcntl_fork
,其在当前进程 fork 一个子进程,然后父子进程在 fork 处分别继续向下执行。
这里需要注意,pcntl_fork
返回的值在父进程会得到子进程的 PID (进程 ID),而在子进程中,该值为 ``。
实例
接着开始实践,执行 pcntl.php 脚本:
$ php ./pcntl.php
Child process #7217 started
Child process #7218 started
Child process #7218 finished
Child process #7220 started
Child process #7221 started
Child process #7219 started
Child process #7221 finished
Child process #7217 finished
Child process #7220 finished
Child process #7219 finished
Child process #7217 exited with status: 0
Child process #7218 exited with status: 0
Child process #7219 exited with status: 0
Child process #7220 exited with status: 0
Child process #7221 exited with status: 0
pcntl.php
<?php
if (!extension_loaded('pcntl')) {
die("Extension not loaded: pcntl\n");
}
$workers = [];
$workersCount = 5;
for ($i = 0; $i < $workersCount; $i++) {
$pid = pcntl_fork();
if ($pid < 0) {
die("Could not fork\n");
}
if ($pid > 0) {
// parent process
$workers[] = $pid; // store child process ID.
continue;
}
// child process
$pid = posix_getpid();
echo "Child process #{$pid} started\n";
// task
sleep(rand(0, 2));
echo "Child process #{$pid} finished\n";
// exit on child process has finished it's task.
exit(0);
}
// parent process
foreach ($workers as $worker) {
// wait child process to exit
pcntl_waitpid($worker, $status);
echo "Child process #{$worker} exited with status: {$status}\n";
}