Body Parsing Middleware

It’s very common in web APIs to send data in JSON or XML format. Out of the box, PSR-7 implementations do not support these formats, you have to decode the Request object’s getBody() yourself. As this is a common requirement, Slim 4 provides BodyParsingMiddleware to handle this task.


It’s recommended to put the body parsing middleware before the call to addErrorMiddlware, so that the stack looks like this:


use Slim\Factory\AppFactory;

require_once __DIR__ . '/../vendor/autoload.php';

$app = AppFactory::create();

// Parse json, form data and xml


$app->addErrorMiddleware(true, true, true);

// ...


Posted JSON, form or XML data

No changes are required to the POST handler because the BodyParsingMiddleware detects that the Content-Type is set to a JSON media type and so places the decoded body into the Request’s parsed body property.

For data posted to the website from a browser, you can use the $request’s getParsedBody() method.

This will return an array of the posted data.

$app->post('/', function (Request $request, Response $response, $args): Response {
    $data = $request->getParsedBody();
    $html = var_export($data, true);
    return $response;

Media type detection

  • The middleware reads the Content-Type from the request header to detect the media type.
  • Checks if this specific media type has a parser registered
  • If not, look for a media type with a structured syntax suffix (RFC 6839), e.g. application/*

Supported media types

  • application/json
  • application/x-www-form-urlencoded
  • application/xml
  • text/xml