Use semaphores to synchronize multiple tasks to practice PHP multi-thread programming

PHP is a very popular server-side scripting language that is widely used in the field of web development. In traditional PHP programming, requests are usually handled in a single-threaded manner. However, in some specific application scenarios, multiple tasks need to be processed at the same time. At this time, multi-threaded programming technology needs to be used to improve the efficiency of the program.

This article will introduce how to implement multi-threaded programming in PHP and use semaphores to synchronize the execution of multiple tasks.

1. Use multi-threading for task processing

In PHP, you can use the PCNTL extension to implement multi-threaded programming. This extension provides a set of methods to create, manage and control multiple child processes. The following is a simple example:

<?php
$taskList = array('task1', 'task2', 'task3');

foreach ($taskList as $task) {
    $pid = pcntl_fork();
    
    if ($pid == -1) {
        die('创建子进程失败');
    } elseif ($pid) {
        // 父进程
        continue;
    } else {
        // 子进程
        // 执行任务
        echo "正在执行任务：".$task."
";
        sleep(5);
        exit(); // 子进程执行完毕后退出
    }
}

// 等待所有子进程结束
while (pcntl_waitpid(0, $status) != -1) {
    $status = pcntl_wexitstatus($status);
    echo "子进程结束，返回值为：" . $status."
";
}

In the above code, we define a task list that contains three tasks. Create a child process through a loop and wait for the child process to end using the pcntl_waitpid method. In the child process, we performed a simple task and created the child process through pcntl_fork.

2. Use semaphores to synchronize the execution of multiple tasks

In multi-thread programming, since multiple tasks are executed at the same time, resource competition may occur. In order to avoid this situation, we can use semaphores to synchronize the execution of multiple tasks.

The PCNTL extension in PHP provides the pcntl_signal and pcntl_wait methods to implement the semaphore mechanism. The following is a sample code:

<?php
declare(ticks = 1);

// 信号处理函数
function signalHandler($signal)
{
    echo "接收到信号：" . $signal . "
";
}

// 注册信号处理函数
pcntl_signal(SIGUSR1, "signalHandler");
pcntl_signal(SIGUSR2, "signalHandler");

$taskList = array('task1', 'task2', 'task3');

// 创建子进程
foreach ($taskList as $task) {
    $pid = pcntl_fork();
    
    if ($pid == -1) {
        die('创建子进程失败');
    } elseif ($pid) {
        // 父进程
        continue;
    } else {
        // 子进程
        echo "正在执行任务：".$task."
";
        sleep(5);
        posix_kill(posix_getppid(), SIGUSR1); // 发送信号告知父进程任务执行完毕
        exit();
    }
}

// 等待所有子进程结束
while (pcntl_waitpid(0, $status) != -1) {
    $status = pcntl_wexitstatus($status);
    echo "子进程结束，返回值为：" . $status."
";
    pcntl_signal_dispatch(); // 分发信号处理函数
}

In the above code, we define a signal processing function signalHandler for receiving and processing signals. Register the signal processing function through the pcntl_signal method. In the child process, we performed a simple task and sent a signal to the parent process through the posix_kill method. In the parent process, we use the pcntl_waitpid method to wait for the child process to end, and use the pcntl_signal_dispatch method to dispatch the signal processing function.

By using semaphores, we can ensure the synchronous execution of multiple tasks and avoid resource competition issues.

3. Summary

This article introduces how to implement multi-threaded programming in PHP and use semaphores to synchronize the execution of multiple tasks. Through PCNTL extension, we can create, manage and control multiple sub-processes to achieve concurrent processing tasks. At the same time, by using semaphores, we can ensure the synchronous execution of multiple tasks and avoid resource competition issues.

Multi-threaded programming is very useful in certain specific application scenarios, which can improve the efficiency and response speed of the program. I hope this article will be helpful to everyone in the practice of PHP multi-threaded programming.

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