How to implement multi-process in php

How to implement multi-process in php: through pcntl and posix extensions. Depending on the needs, we can use the pcntl_fork() function to create a child process and the pcntl_wait() function to block the current process.

#php multi-process requires pcntl, posix extension support.

Multi-process implementation can only be done in cli mode. In a web server environment, unexpected results may occur.

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Multi-process core function:

pcntl_fork (create child process), pcntl_wait( Block the current process)

Detailed introduction:

pcntl_fork:

A call returns twice, the child process pid is returned in the parent process, 0 is returned in the child process, and -1 is returned on error.

pcntl_wait ( int &$status [, int $options ] )：

Block the current process until any child process exits or receives a signal to end the current process. Note that it is a signal to end the current process, and the SIGCHLD sent by the child process to end is not counted. Use $status to return the status code of the child process, and you can specify the second parameter to indicate whether it is called in a blocking state.

The function return value is the pid of the child process. If there is no child process, the return value is Is -1;

Called in non-blocking mode, the function can also return 0 when a child process is running but has not ended.

pcntl_waitpid ( int $pid , int &$status [, int $options ] )

The function is the same as pcntl_wait, the difference is that waitpid is the child process waiting for the specified pid. When pid is -1, pcntl_waitpid is the same as pcntl_wait. The status information of the child process is stored in $status in the pcntl_wait and pcntl_waitpid functions.

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Example:

A fixed number of child processes are always running in

php.

Use core functions such as pcntl_fork (create child process), pcntl_wait (block the current process) as needed

###Code implementation: ###

<?php

//最大的子进程数量
$maxChildPro = 8;

//当前的子进程数量
$curChildPro = 0;

//当子进程退出时，会触发该函数,当前子进程数-1
function sig_handler($sig)
{
    global $curChildPro;
    switch ($sig) {
        case SIGCHLD:
            echo &#39;SIGCHLD&#39;, PHP_EOL;
            $curChildPro--;
            break;
    }
}

//配合pcntl_signal使用，简单的说，是为了让系统产生时间云，让信号捕捉函数能够捕捉到信号量
declare(ticks = 1);

//注册子进程退出时调用的函数。SIGCHLD：在一个进程终止或者停止时，将SIGCHLD信号发送给其父进程。
pcntl_signal(SIGCHLD, "sig_handler");

while (true) {
    $curChildPro++;
    $pid = pcntl_fork();
    if ($pid) {
//父进程运行代码,达到上限时父进程阻塞等待任一子进程退出后while循环继续
        if ($curChildPro >= $maxChildPro) {
            pcntl_wait($status);
        }
    } else {
//子进程运行代码
        $s = rand(2, 6);
        sleep($s);
        echo "child sleep $s second quit", PHP_EOL;
        exit;
    }
}

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