Can PHP Really Multithread? The pthreads Solution Explained

Multithreading in PHP: Is It Possible?

The question of whether multithreading is possible in PHP has been a long-standing one, with past suggestions of forcing multiple PHP instances on the operating system. However, this approach posed issues of memory utilization and process termination.

Introducing pthreads

The answer lies in the pthreads extension, which provides a robust object-oriented API for multithreading in PHP. This extension is available in PHP 7.2 and requires CLI-based applications, as multithreading is not supported in web server environments.

Using pthreads

The pthreads extension provides classes such as Thread, Workers, and Threaded objects to manage threads, execute tasks concurrently, and synchronize execution.

Simple Example

Consider the following code snippet:

class AsyncOperation extends Thread {
    public function run() {
        // Long-running operation
    }
}

$stack = array();
foreach (range("A", "D") as $i) {
    $stack[] = new AsyncOperation($i);
}

foreach ($stack as $t) {
    $t->start();
}

This code creates multiple threads and executes them simultaneously, outputting timestamps and task statuses.

Real-World Example

A practical application of multithreading in PHP is making asynchronous web requests:

class AsyncWebRequest extends Thread {
    public function run() {
        $this->data = file_get_contents($this->url);
    }
}

$g = new AsyncWebRequest(sprintf("http://www.google.com/?q=%s", rand() * 10));
$g->start();

while ($g->isRunning()) {
    echo ".";
    usleep(100);
}

if ($g->join()) {
    printf("Request took %f seconds to finish receiving %d bytes\n", microtime(true) - $t, strlen($g->data));
}

This code starts an asynchronous web request, prints dots during the process, and logs the time taken to receive the response.

Conclusion

With the pthreads extension, PHP provides a powerful mechanism for multithreading, allowing developers to concurrently execute tasks and improve the performance of CLI-based applications.

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