PHP支持並發(fā)和異步操作，但方式不同於Node.js或Go。 1.可通過ReactPHP或Amp實現(xiàn)異步I/O，適用於處理多HTTP請求、實時消息等I/O密集型任務(wù)；2.使用pcntl_fork()可在CLI模式下通過多進(jìn)程實現(xiàn)並行處理，適合批處理任務(wù)；3.雖有pthreads擴展支持線程，但僅限CLI環(huán)境且受限較多，Web應(yīng)用中不常用。這些方法各有權(quán)衡，雖不如Go等語言原生支持強，但在合適場景下仍能提升性能。

PHP wasn't originally built with concurrency or asynchronous operations in mind. It was designed for simple, synchronous request-response web interactions. But as web applications have grown more complex, PHP has evolved to support concurrency and async behavior — though not in the same way as Node.js or Go.

Let's break down how PHP handles these things today.

Using Multi-Threading with pthreads (Limited Use)

PHP itself is not multi-threaded by default. However, there's an extension called pthreads that allows you to create threads in userland code — but only when running PHP in CLI mode with a special build (like ZTS - Zend Thread Safety enabled).

Example use:

 class MyThread extends Thread {
    public function run() {
        echo "Doing work in thread\n";
    }
}
$t = new MyThread();
$t->start();

However, this approach is not commonly used in traditional web apps because:

• Most PHP runs on Apache or FPM, which are process-based, not thread-safe.
• You can't safely use pthreads inside a web server context.
• Extensions and libraries may not be thread-safe either.

So while threading exists in some environments, it's not something most PHP developers rely on day-to-day.

Leveraging Asynchronous Libraries Like ReactPHP or Amp

To do real async I/O in PHP, people often turn to event-driven frameworks like ReactPHP or Amp .

These libraries let you perform non-blocking operations — like making multiple HTTP requests at once or reading/writing files without blocking execution.

For example, with ReactPHP:

 $loop = React\EventLoop\Factory::create();

$loop->addTimer(1.0, function () {
    echo "One second passed\n";
});

$loop->run();

This lets you write async-style code, but under the hood, it's still single-threaded and uses callbacks or coroutines. You're not truly doing parallel work — just managing many I/O operations concurrently.

Use cases include:

• Building command-line tools that need to handle many connections
• Real-time messaging systems
• Background job workers that talk to APIs or databases

Just keep in mind: async PHP isn't magic. It helps with I/O-bound tasks, but CPU-heavy operations will still block everything else unless offloaded.

Running Concurrent Tasks via Multiple Processes

If you're working in CLI and want true parallelism, forking processes is a common workaround.

Using pcntl_fork() or tools like Symfony Process , you can start multiple child processes that run independently.

Basic fork example:

 $pid = pcntl_fork();

if ($pid == -1) {
    die("Could not fork");
} elseif ($pid == 0) {
    // Child process
    echo "Child doing work\n";
    exit();
} else {
    // Parent waits for child
    pcntl_wait($status);
    echo "Child done\n";
}

This works well for batch jobs or scripts that need to run independent tasks in parallel. Just remember that each process gets its own memory space — so it's heavier than async I/O but more powerful than threading in PHP.

Wrapping Up

In short, PHP doesn't handle concurrency like languages built for it from the ground up. But depending on your needs, you can choose between:

• Async I/O using ReactPHP or Amp for I/O-bound tasks
• Multi-process scripting with pcntl_fork() for CLI parallelism
• Threading with pthreads (in limited contexts)

Each option has trade-offs, and none fully replicates what you'd get in Go or Rust. But for many PHP apps, especially those focused on web requests, these tools can still offer meaningful performance gains when used wisely.

基本上就這些。

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