如果你想继续处理原始的cURL请求，你可以看看异步的curl_multi_*函数--说实话，我已经有一段时间没有直接使用cURL了，所以我只参考PHP docs，它也提供了一个使用示例，你可以把它用作模板。
但是，我建议采用的方法是使用google/auth PHP库，Guzzle HTTP Client进行身份验证并将请求发送到FCM API，Guzzle Promises异步执行请求。
为了使事情变得“更糟”，您不仅必须使用HTTP V1端点，还必须使用HTTP V1 FCM消息格式。下面的代码显示了您原始帖子中的消息将如何更改。
所以，下面是我如何在Composer的帮助下在一个脚本中从头开始：

# Initialize the project
mkdir myproject
cd myproject
composer require google/auth

<?php
# run.php

# This example uses Google Application Credentials exposed via the
# `GOOGLE_APPLICATION_CREDENTIALS` environment variable
# See https://github.com/googleapis/google-auth-library-php/blob/main/README.md
# for more alternative ways to authenticate requests

declare(strict_types=1);

require 'vendor/autoload.php';

use Google\Auth\ApplicationDefaultCredentials;
use GuzzleHttp\Client;
use GuzzleHttp\HandlerStack;
use GuzzleHttp\Promise;

### Create a Guzzle client that authenticates requests to the FCM API Endpoints

putenv('GOOGLE_APPLICATION_CREDENTIALS=/path/to/my/credentials.json');

// https://developers.google.com/identity/protocols/oauth2/scopes#fcm
$scopes = [
    'https://www.googleapis.com/auth/cloud-platform',
    'https://www.googleapis.com/auth/firebase.messaging',
];

// create middleware
$middleware = ApplicationDefaultCredentials::getMiddleware($scopes);
$stack = HandlerStack::create();
$stack->push($middleware);

$client = new Client([
  'handler' => $stack,
  'auth' => 'google_auth'
]);

### Setup the messages

$deviceTokens = [/* ... */];
$messages = [];

foreach ($deviceTokens as $token) {
    $messages[] = [
        'token' => $token,
        'notification' => [
            'title' => 'Notification Title',
            'body' => 'Notification Body',
            'image' => 'https://example.com/test.jpg',
        ],
        'webpush' => [
            'fcm_options' => [
                'link' => 'https://example.com'
            ],
        ],
    ];
}

### Create message request promises

$promises = function() use ($client, $messages) {
    foreach ($messages as $message) {
        yield $client->requestAsync('POST', 'https://fcm.googleapis.com/v1/projects/my-app/messages:send', [
            'json' => ['message' => $message],
        ]);
    }
};

### Create response handler

$handleResponses = function (array $responses) {
    foreach ($responses as $response) {
        if ($response['state'] === Promise\PromiseInterface::FULFILLED) {
            // $response['value'] is an instance of \Psr\Http\Message\RequestInterface
            echo $response['value']->getBody();
        } elseif ($response['state'] === Promise\PromiseInterface::REJECTED) {
            // $response['reason'] is an exception
            echo $response['reason']->getMessage();
        }
    }
};

Promise\Utils::settle($promises())
    ->then($handleResponses)
    ->wait();

我用一个有效的和一个无效的注册令牌测试了这个脚本，得到了以下结果：

❯ php run.php
Client error: `POST https://fcm.googleapis.com/v1/projects/beste-firebase/messages:send` resulted in a `400 Bad Request` response:
{
  "error": {
    "code": 400,
    "message": "The registration token is not a valid FCM registration token",
    "stat (truncated...)
{
  "name": "projects/beste-firebase/messages/e39032c2-866d-4263-83e6-b1ce3770dfe6"
}

或者，如果您不想手动完成所有这些操作，也可以使用（非官方的）Firebase Admin PHP SDK，它在其最新的7.5.0版本中切换到这种方法。（免责声明：我是维护者，显然有偏见）：

# Initialize the project
mkdir myproject
cd myproject
composer require kreait/firebase-php

<?php
# run.php

# Again, this example uses Google Application Credentials exposed via the
# `GOOGLE_APPLICATION_CREDENTIALS` environment variable. The SDK picks
# them up automatically.

declare(strict_types=1);

require 'vendor/autoload.php';

use Kreait\Firebase\Factory;

### Initialize FCM
putenv('GOOGLE_APPLICATION_CREDENTIALS=/path/to/my/credentials.json');
$fcm = (new Factory())->createMessaging();

### Setup the message (without target)

$deviceTokens = [/* ... */];
$message = [
    'notification' => [
        'title' => 'Notification Title',
        'body' => 'Notification Body',
        'image' => 'https://example.com/test.jpg',
    ],
    'webpush' => [
        'fcm_options' => [
            'link' => 'https://example.com'
        ],
    ],
];

### Send the message to the given tokens

$reports = $fcm->sendMulticast($message, $deviceTokens);

# https://firebase-php.readthedocs.io/en/stable/cloud-messaging.html#send-messages-to-multiple-devices-multicast
# goes more into detail what you can do with the reports

我希望这对你有帮助！