Multithreading in PHP and how to implement it

Multi-threading refers to running multiple threads (program execution flow) at the same time in an application, and can perform multiple tasks at the same time. In PHP, multi-threading is widely used in scenarios that require multiple tasks to be performed simultaneously, such as big data calculations, concurrent access, etc. This article will introduce multi-threading in PHP and how to implement it.

1. PHP multi-threading implementation principle

Before truly understanding the PHP multi-threading implementation method, there is a concept that needs to be understood, and that is the relationship between processes and threads. A process refers to a running program instance. Each process has its own memory space and resources, and processes are independent of each other. A thread is an executable unit within a process. A process can contain multiple threads and share the resources of the process. The advantage of multi-threading over multi-process is that switching between threads is faster than switching between processes, and the resource overhead is smaller. It is suitable for scenarios such as concurrent access that require the execution of multiple tasks at the same time.

In PHP, to implement multi-threading, you need to use an extension called "PCNTL" library. This extension provides a set of functions that can control processes and signal handling, enabling multi-process and multi-thread programming.

2. How to implement multi-threading in PHP

1. Use the pcntl_fork() function to create a child process

Use the pcntl_fork() function in PHP to create a child process. The current process is copied into two processes, one is the parent process and the other is the child process. The parent process and the child process are two independent processes, but they share some resources. This feature can be used to implement multi-threading.

The following is an example, creating 5 sub-processes, each sub-process performs different tasks:

<?php
$workers = 5;

for ($i = 0; $i < $workers; $i++) {
    $pid = pcntl_fork();
    if ($pid === -1) {
        die('Could not fork');
    } elseif ($pid) {
        // 父进程继续执行
    } else {
        // 子进程执行任务
        sleep(5);
        exit(0);
    }
}

// 父进程等待所有子进程结束
while (pcntl_waitpid(0, $status) != -1) {
    $status = pcntl_wexitstatus($status);
    echo "Child $status completed
";
}
?>

2. Use the pcntl_signal() function to implement signal processing

In multi-threading In order to avoid conflicts between different threads, a signal processing mechanism needs to be used to handle synchronization issues in multi-threads.

Use the pcntl_signal() function in PHP to set the signal processing method. The following is an example, creating 5 child processes, each child process performs different tasks. When all child processes have completed their tasks, the parent process will continue to execute:

<?php
$workers = 5;
$jobs = [];

// 子进程任务
function doJob($job) {
    echo "Worker $job start
";
    sleep(5);
    echo "Worker $job completed
";
}

// 信号处理函数
function sig_handler($signo) {
    global $jobs;
    switch ($signo) {
        case SIGCHLD:
            // 检查所有子进程是否都已经结束
            while (($pid = pcntl_waitpid(-1, $status, WNOHANG)) > 0) {
                $jobs--;
            }
            break;
    }
}

// 安装信号处理器
pcntl_signal(SIGCHLD, "sig_handler");

// 创建子进程
for ($i = 0; $i < $workers; $i++) {
    $pid = pcntl_fork();
    if ($pid == -1) {
        die('Could not fork');
    } elseif ($pid == 0) {
        // 子进程执行任务
        doJob($i);
        exit(0);
    } else {
        // 父进程继续执行
        $jobs++;
    }
}

// 父进程等待所有子进程结束
while ($jobs > 0) {
    sleep(1);
}

// 所有子进程都已完成任务
echo "All workers completed
";
?>

The above is how PHP implements multi-threading. You can Choose according to actual needs.

3. Summary

The multi-threading implementation method in PHP mainly relies on the extension of the "PCNTL" library, using the pcntl_fork() function to create a child process, and using the pcntl_signal() function to implement signal processing. In multi-threaded programming, you need to pay attention to synchronization issues and synchronize processing between different threads to avoid conflicts.

The above is the detailed content of Multithreading in PHP and how to implement it. For more information, please follow other related articles on the PHP Chinese website!