PSR-7 defines common interfaces for representing HTTP messages in PHP. These interfaces enable framework-agnostic HTTP message handling, making it easier to create interoperable HTTP clients, servers, and middleware.
Core Interfaces
1. Message Interface
<?php
namespace Psr\Http\Message;
interface MessageInterface
{
public function getProtocolVersion();
public function withProtocolVersion($version);
public function getHeaders();
public function hasHeader($name);
public function getHeader($name);
public function getHeaderLine($name);
public function withHeader($name, $value);
public function withAddedHeader($name, $value);
public function withoutHeader($name);
public function getBody();
public function withBody(StreamInterface $body);
}
2. Request Interface
<?php
namespace Psr\Http\Message;
interface RequestInterface extends MessageInterface
{
public function getRequestTarget();
public function withRequestTarget($requestTarget);
public function getMethod();
public function withMethod($method);
public function getUri();
public function withUri(UriInterface $uri, $preserveHost = false);
}
3. Response Interface
<?php
namespace Psr\Http\Message;
interface ResponseInterface extends MessageInterface
{
public function getStatusCode();
public function withStatus($code, $reasonPhrase = '');
public function getReasonPhrase();
}
Basic Implementation
1. Creating Requests
<?php
use GuzzleHttp\Psr7\Request;
use GuzzleHttp\Psr7\Uri;
// Simple GET request
$request = new Request(
'GET',
'https://api.example.com/users'
);
// POST request with JSON body
$request = new Request(
'POST',
'https://api.example.com/users',
[
'Content-Type' => 'application/json'
],
json_encode(['name' => 'John Doe'])
);
2. Handling Responses
<?php
use GuzzleHttp\Psr7\Response;
$response = new Response(
200,
['Content-Type' => 'application/json'],
json_encode(['status' => 'success'])
);
// Working with responses
$status = $response->getStatusCode();
$body = $response->getBody()->getContents();
$contentType = $response->getHeaderLine('Content-Type');
HTTP Client Implementation
<?php
class HttpClient
{
public function sendRequest(RequestInterface $request): ResponseInterface
{
$context = stream_context_create([
'http' => [
'method' => $request->getMethod(),
'header' => $this->formatHeaders($request->getHeaders()),
'content' => (string) $request->getBody(),
'protocol_version' => $request->getProtocolVersion(),
'ignore_errors' => true,
],
]);
$body = file_get_contents($request->getUri(), false, $context);
$response = new Response(
$this->getStatusCode($http_response_header),
$this->parseHeaders($http_response_header),
$body
);
return $response;
}
private function formatHeaders(array $headers): string
{
$lines = [];
foreach ($headers as $name => $values) {
$lines[] = $name . ': ' . implode(', ', $values);
}
return implode("\r\n", $lines);
}
// Additional helper methods...
}
Middleware Pattern
<?php
interface MiddlewareInterface
{
public function process(
RequestInterface $request,
RequestHandlerInterface $handler
): ResponseInterface;
}
class LoggingMiddleware implements MiddlewareInterface
{
public function process(
RequestInterface $request,
RequestHandlerInterface $handler
): ResponseInterface {
// Log request
$response = $handler->handle($request);
// Log response
return $response;
}
}
Framework Integration
1. Laravel Example
<?php
use Illuminate\Http\Request;
use Psr\Http\Message\ServerRequestInterface;
use Symfony\Bridge\PsrHttpMessage\Factory\PsrHttpFactory;
class PsrBridge
{
public function toServerRequest(Request $request): ServerRequestInterface
{
$psr17Factory = new Psr17Factory();
$psrHttpFactory = new PsrHttpFactory($psr17Factory, $psr17Factory, $psr17Factory, $psr17Factory);
return $psrHttpFactory->createRequest($request);
}
}
2. Symfony Example
<?php
use Symfony\Bridge\PsrHttpMessage\Factory\HttpFoundationFactory;
use Symfony\Bridge\PsrHttpMessage\Factory\PsrHttpFactory;
// Convert PSR-7 to Symfony
$httpFoundationFactory = new HttpFoundationFactory();
$symfonyRequest = $httpFoundationFactory->createRequest($psrRequest);
// Convert Symfony to PSR-7
$psr17Factory = new Psr17Factory();
$psrHttpFactory = new PsrHttpFactory($psr17Factory, $psr17Factory, $psr17Factory, $psr17Factory);
$psrRequest = $psrHttpFactory->createRequest($symfonyRequest);
Best Practices
- Immutability
// Bad - Modifying message directly
$request->method = 'POST';
// Good - Using withers
$newRequest = $request->withMethod('POST');
- Stream Handling
// Bad - Loading entire body into memory
$content = $request->getBody()->getContents();
// Good - Streaming large responses
$body = $response->getBody();
while (!$body->eof()) {
echo $body->read(8192);
}
Common Patterns
1. Request Builder
<?php
class RequestBuilder
{
private $method = 'GET';
private $uri;
private $headers = [];
private $body;
public function method(string $method): self
{
$this->method = $method;
return $this;
}
public function uri(string $uri): self
{
$this->uri = new Uri($uri);
return $this;
}
public function build(): RequestInterface
{
return new Request(
$this->method,
$this->uri,
$this->headers,
$this->body
);
}
}
2. Response Factory
<?php
class ResponseFactory
{
public static function json(
$data,
int $status = 200,
array $headers = []
): ResponseInterface {
return new Response(
$status,
array_merge(
['Content-Type' => 'application/json'],
$headers
),
json_encode($data)
);
}
}
Next Steps
In our next post, we’ll explore PSR-15, which builds upon PSR-7 to define HTTP server request handlers and middleware. Check out our example repository for the implementation of these standards.
Resources
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