Is there an asynchronous http request related class in PHP?

PHP traditionally executes code synchronously, meaning that each line of code is executed one after the other, and the program waits for each operation to complete before moving on to the next one. However, there have been efforts to introduce asynchronous programming capabilities in PHP.

One such effort is the introduction of asynchronous features in PHP 7.1 and later versions through the `async` and `await` keywords. Asynchronous programming allows non-blocking execution of code, which can be beneficial for tasks such as making asynchronous HTTP requests.

In terms of making asynchronous HTTP requests, there are libraries and extensions that provide asynchronous functionality. One notable library is `ReactPHP`, which is a low-level library for event-driven programming in PHP. It includes components for handling asynchronous HTTP requests.

Here's a simplified example using ReactPHP:

```php
require 'vendor/autoload.php';

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

$client = new React\Http\Browser($loop);

$promises = [
    $client->get('http://example.com'),
    $client->get('http://example.org'),
];

React\Promise\all($promises)->then(
    function ($responses) {
        foreach ($responses as $response) {
            echo $response->getBody();
        }
    },
    function (Exception $exception) {
        echo 'Error: ' . $exception->getMessage();
    }
);

$loop->run();
```

In this example, ReactPHP's `Browser` class is used to make asynchronous HTTP requests. The `React\Promise\all` function is used to handle multiple asynchronous requests, and the `then` method is used to process the responses.

Keep in mind that the landscape of asynchronous programming in PHP may evolve, and new libraries or features might be introduced. Always refer to the official documentation and community resources for the latest information on asynchronous programming in PHP. Additionally, check for updates beyond my last knowledge update in January 2022.