New in Symfony 4.3: HttpClient component

Basic usage

The Symfony\Component\HttpClient\HttpClient class provided to make HTTP requests is quite straightforward:

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use Symfony\Component\HttpClient\HttpClient;

$httpClient = HttpClient::create();
$response = $httpClient->request('GET', 'https://api.github.com/repos/symfony/symfony-docs');

A significant difference with other existing HTTP clients is that the request() call is not blocking. In other words, the $response object is available immediately and the code execution can continue.

Later, when you call to getStatusCode(), the code execution will stop until the headers are available and when you call to getContent(), it will stop until the full contents are available (but you can use Streaming responses):

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$statusCode = $response->getStatusCode();
// $statusCode = 200
$content = $response->getContent();
// returns the raw content returned by the server (JSON in this case)
// $content = '{"id":521583, "name":"symfony-docs", ...}'
$content = $response->toArray();
// transforms the response JSON content into a PHP array
// $content = ['id' => 521583, 'name' => 'symfony-docs', ...]

Thanks to this non-blocking behavior, you can make multiple calls to request() to perform parallel requests and then access the info of the responses only after starting all requests.

By default, the component uses native PHP functions to make the HTTP requests, so you don't have to install any other dependency. However, it will use the cURL based transport if your system has both the cURL library and the PHP cURL extension installed.

When the HTTP status code of the response is not in the 200-299 range (i.e. 3xx, 4xx or 5xx) your code is expected to handle it. If you don't do that, the getHeaders() and getContent() methods throw an appropriate exception:

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// the response of this request will be a 403 HTTP error
$response = $httpClient->request('GET', 'https://httpbin.org/status/403');

// this code results in a Symfony\Component\HttpClient\Exception\ClientException
// because it doesn't check the status code of the response
$content = $response->getContent();

// do this instead
if (200 !== $response->getStatusCode()) {
    // handle the HTTP request error (e.g. retry the request)
} else {
    $content = $response->getContent();
}

Features

The new HttpClient component is packed with useful features. All of them are explained in the docs:

• Support for HTTP Basic and HTTP Bearer authentications;
• Support for adding custom query string parameters and custom HTTP headers;
• Allow to upload data using strings, closures and PHP resources;
• Streaming responses to get chunks of the response sequentially instead of waiting for the entire response;
• Request and response caching;
• Scoping HTTP clients to auto-configure the client based on the requested URL;
• PSR-7 and PSR-18 Compatibility;
• MockHttpClient to simplify testing requests and responses.

Symfony framework integration

When using HttpClient inside a full Symfony application instead of as a stand-alone component, you can configure it under the http_client key (check out the full HttpClient configuration reference):

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# config/packages/framework.yaml
framework:
    # ...
    http_client:
        max_redirects: 7
        max_host_connections: 10

Then, you can inject the HttpClient in other services as follows:

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use Symfony\Contracts\HttpClient\HttpClientInterface;

class SomeService
{
    private $httpClient;

    public function __construct(HttpClientInterface $httpClient)
    {
        $this->httpClient = $httpClient;
    }
}

Future integrations

Having a default and official HTTP client for Symfony applications will allow us to implement other features that require communicating with third-party services. A recent example of this is the NotCompromisedPassword validator, which makes your applications more secure and uses the HttpClient component to make the HTTP requests required to check if a given password was publicly compromised or not.

In addition, the Mercure component is also switching their current HTTP client by the new HttpClient component (see PR #8). Finally, API Platform is going to introduce a new set of API testing utilities built with the HttpClient component (see PR #2608).