A preliminary study on concurrent programming in PHP: multi-threading, coroutines, etc.

In network applications, servers usually need to handle multiple requests at the same time, and concurrent programming has become a very important topic. As a very popular web development language, PHP's concurrent programming has also attracted much attention. This article will introduce multi-threading, coroutine and other concurrent programming methods in PHP.

1. Multi-threading

In PHP, we can implement multi-threaded programming through extensions. Here we introduce PThreads, an extension of PHP.

PThreads provides complete multi-threading support for PHP. It provides multi-thread creation, lock and synchronization, thread pool and other functions. The following is a simple example:

class MyThread extends Thread {
    public function run() {
        echo "Hello World
";
    }
}

$myThread = new MyThread();
$myThread -> start();
$myThread -> join();

In the above code, we created a MyThread class that inherits Thread, and defined the multi-threaded tasks we need to run in the run method, calling the start() method to start the thread, and the join() method indicates that the main thread can continue to execute only after the thread has finished running. Here we just output a simple sentence. In actual applications, you can write your own multi-threaded tasks as needed.

It should be noted that PThreads will cease maintenance after PHP7.2, so version compatibility issues need to be considered when using it.

2. Coroutine

Compared with multi-threading, coroutine is a more lightweight concurrent programming method. In PHP, we can support it through Swoole and other extensions. Coroutine programming.

Swoole's coroutine mode uses a signal-based coroutine scheduler, which can support large-scale coroutine concurrency. The following is a simple example:

Coun(function() {
    Co::create(function() {
        echo "Hello";
    });
    Co::create(function() {
        echo "World";
    });
});

In the above code, we use Swoole's Co coroutine, start the coroutine through the Coun() method, and use the Co::create() method to create the coroutine. process, we output a sentence in each coroutine.

It should be noted that although coroutines are lightweight, you need to pay attention to memory leaks when using them. You also need to pay attention to synchronization and mutual exclusion issues between coroutines.

3. Asynchronous

In addition to multi-threading and coroutines, asynchronous programming is also a common concurrent programming method. In PHP, we can implement asynchronous programming by providing extensions that provide asynchronous IO support, such as swoole, etc.

The following is an example of asynchronous programming using swoole:

$http = new swoole_http_server("0.0.0.0", 9501);
$http->on("request", function ($request, $response) {
    $response->header("Content-Type", "text/plain");
    $response->end("Hello World
");
});
$http->start();

In the above code, we use swoole's asynchronous IO support to create an HTTP server and use the on() method to Register an event callback function and execute the code in the callback function when there is a request.

Summary

This article introduces three common concurrent programming methods in PHP: multi-threading, coroutine and asynchronous programming. It should be noted that different concurrent programming methods have their own advantages and disadvantages, and the appropriate method should be selected according to the specific scenario. At the same time, when using these extensions, you also need to pay attention to issues such as compatibility and stability.

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