Embracing PSRs to build an interoperable Http Client

Learn to build a PSR-18 compliant HTTP client in PHP, enhancing web development through interoperability and efficient request handling.

Embracing PSRs to build an interoperable Http Client
Embracing PSRs to build an interoperable Http Client

Recently I have been scratching my head over PSR-18. As a new PSR there isn’t a lot of information around it, but I saw that as a challenge. I decided to accept this challenge and build a compliant HTTP client to embrace the future of interoperability.

If you look at the specifications for PSR-18 on PHP-FIG they are typically pretty confusing, but I read between the lines a little. The first step was to build a class that would accept all the necessary components to bootstrap the client.

namespace JustSteveKing\HttpSlim;

use Psr\Http\Message\StreamFactoryInterface;
use Psr\Http\Message\RequestFactoryInterface;
use Psr\Http\Client\ClientExceptionInterface;

class HttpClient implements HttpClientInterface
  protected ClientInterface $client;
  protected StreamFactoryInterface $streamFactory;
  protected RequestFactoryInterface $requestFactory;

Now if you have read any of my other posts, or used any of my packages, or seen my posts on twitter, you will know I am a huge fan of named constructors.

final protected function __construct(
  ClientInterface $client,
  RequestFactoryInterface $requestFactory,
  StreamFactoryInterface $streamFactory
) {
  $this->client = $client;
  $this->requestFactory = $requestFactory;
  $this->streamFactory = $streamFactory;

public static function build(
  ClientInterface $client,
  RequestFactoryInterface $requestFactory,
  StreamFactoryInterface $streamFactory
): self {
  return new static(

This gives us a good starting point to begin with, from here we can implement our helper methods for making requests and encoding json. Our helper methods follow a typical pattern of, take a URL and an optional body as an array - making sure that we return a PSR-7 compliant Response (but that it typically down to the client library we inject). Here is an example of the post request:

use \JsonException;
use Psr\Http\Message\ResponseInterface;
use JustSteveKing\HttpSlim\Exceptions\RequestError;

public function post(string $uri, array $body): ResponseInterface
  // build out json body content
  try {
    $content = $this->encodeJson($body);
  } catch (JsonException $exception) {
    throw RequestError::invalidJson($exception); 

  $request = $this->requestFactory
    ->createRequest('POST', $uri)
    ->withAddedHeader('Content-Type', 'application/json')

  return $this->client->sendRequest($request);

Our encodeJson method simply returns a json encoded version of the passed through array.

This is just one adventure into embracing PSRs, but I have thoroughly enjoyed it so far! Please drop me a tweet if you have found this useful at all, or if you find an issue - feel free to drop an issue on the GitHub repo