告别阻塞与回调地狱：如何使用Composer和GuzzlePromises优化PHP异步操作

<code class="php">$userId = call_external_api_get_user_id(); // 阻塞等待
$userDetails = call_external_api_get_user_details($userId); // 阻塞等待
$userOrders = call_external_api_get_user_orders($userId); // 阻塞等待

// ... 处理数据 ...</code>

<code class="bash">composer require guzzlehttp/promises</code>

<code class="php">use GuzzleHttp\Promise\Promise;

// 模拟异步操作A：获取用户ID
function getUserIdAsync(): Promise
{
    $promise = new Promise();
    // 假设这是一个耗时操作，例如发起HTTP请求
    go(function () use ($promise) { // 在Swoole/Hyperf环境下，可以使用go协程
        sleep(1); // 模拟耗时
        $promise->resolve('user_123'); // 成功获取用户ID
    });
    return $promise;
}

// 模拟异步操作B：根据用户ID获取用户详情
function getUserDetailsAsync(string $userId): Promise
{
    $promise = new Promise();
    go(function () use ($promise, $userId) {
        sleep(1); // 模拟耗时
        $details = ['id' => $userId, 'name' => 'Alice', 'email' => 'alice@example.com'];
        $promise->resolve($details); // 成功获取用户详情
    });
    return $promise;
}

// 模拟异步操作C：根据用户ID获取订单列表
function getUserOrdersAsync(string $userId): Promise
{
    $promise = new Promise();
    go(function () use ($promise, $userId) {
        sleep(1); // 模拟耗时
        $orders = [['order_id' => 'ORD001'], ['order_id' => 'ORD002']];
        $promise->resolve($orders); // 成功获取订单列表
    });
    return $promise;
}

// 链式调用
$startTime = microtime(true);

getUserIdAsync()
    ->then(function ($userId) {
        echo "Step 1: Got User ID: " . $userId . "\n";
        return getUserDetailsAsync($userId); // 返回一个新的Promise，链条继续
    })
    ->then(function ($userDetails) {
        echo "Step 2: Got User Details: " . json_encode($userDetails) . "\n";
        return getUserOrdersAsync($userDetails['id']); // 返回一个新的Promise
    })
    ->then(function ($userOrders) {
        echo "Step 3: Got User Orders: " . json_encode($userOrders) . "\n";
        echo "All operations completed successfully!\n";
    })
    ->otherwise(function ($reason) { // 统一处理链条中的任何拒绝（错误）
        echo "An error occurred: " . $reason . "\n";
    })
    ->wait(); // 同步等待所有Promise完成并获取最终结果

$endTime = microtime(true);
echo "Total time: " . round($endTime - $startTime, 2) . " seconds\n";</code>

<code class="php">use GuzzleHttp\Promise\Utils;
// ... (你的Promise定义) ...

// 在事件循环中运行任务队列
// $loop = React\EventLoop\Factory::create();
// $loop->addPeriodicTimer(0, [Utils::queue(), 'run']);
// $loop->run(); // 启动事件循环</code>