Slim 4.0.0-alpha released

We are excited to announce the Slim 4.0.0 alpha release. Please direct all your feedback for this release to the Slim 4 Alpha Release Feedback Thread. The new docs are located here.

General Direction

For this major release the focus was on the following:

  • Implementing PSR-15 Middleware Support
  • Decoupling our dependency on Slim’s PSR-7 implementation and enabling usage of any PSR-7 implementation
  • Decoupling our dependency on Pimple and enabling usage of any PSR-11 ContainerInterface implementation
  • Decoupling our dependency on FastRoute and implement interfaces enabling the user to use any routing library
  • Decoupling error handling from the core and enable users to easily use their own implementations
  • Decoupling response emitting from the core and enable users to easily use their own implementation
  • Remove all traits for a cleaner call stack trace when debugging
  • Create an app factory that makes it easier to create an App instance due to the higher complexity of the increased modularity

Major Changes

  • Slim requires PHP 7.1 or higher.
  • Slim no longer ships with a PSR-7 Implementation.
  • Slim no longer ships with Pimple.
  • Slim no longer sets the default_mimetype to an empty string, so you need to set it yourself in php.ini or your app using ini_set('default_mimetype', '').
  • Slim App::$settings have been removed, multiple middleware have been implemented to replace the functionality from each individual settings.
  • Routing is now done via the Slim\Middleware\RoutingMiddleware. By default routing will be performed last in the middleware queue. If you want to access the route and routingResults attributes from $request you will need to add this middleware last as it will get executed first within the queue when running the app. The middleware queue is still being executed in Last In First Out (LIFO) order. This replaces the determineRouteBeforeAppMiddleware setting.
  • Output buffering is now done via Slim\Middleware\OutputBufferingMiddleware. This replaces the outputBuffering setting.
  • Content length header calculation is now done via Slim\Middleware\ContentLengthMiddleware. This replaces the addContentLengthHeader setting.
  • The RouterInterface component has been split into 4 interfaces RouteCollectorInterface, RouteParserInterface, RouteResolverInterface and DispatcherInterface.
  • Double-Pass middleware has been deprecated. Middleware signature is now the PSR-15 MiddlewareInterface signature process(Request $request, RequestHandler $handler). We no longer support the double-pass function ($request, $response, $next) signature. You can still use callables with the signature function (Request $request, RequestHandler $handler) {} to create middleware or use an invokable class with that signature.
  • Slim App now implements the PSR-15 RequestHandlerInterface. Use $app->handle($request) instead of $app($request).
  • PSR-15 RequestHandler can now be used as route callables.
  • Binding of $app to the RouteGroup callable has been removed. RouteCollectorProxy gets injected into the RouteGroup’s callable instead. $app->group('/group', function (RouteCollectorProxy $group) { $group->get(...); }
  • The App::subRequest() method has been removed. You can perform sub-requests via $app->handle($request) from within a route callable.
  • Removed SlimException. New HttpException have been implemented, namely HttpBadRequestException, HttpForbiddenException, HttpInternalServerErrorException, HttpMethodNotAllowedException, HttpNotFoundException, HttpNotImplementedException and HttpUnauthorizedException. You can also create your own by extending HttpException or HttpSpecializedException.
  • Request method names are now case-sensitive when user App::map().
  • All traits have been removed. CallableResolverTrait and MiddlewareAwareTrait no longer exist.
  • Two new factories have been introduced. AppFactory and ServerRequestCreatorFactory to facilitate App and ServerRequest creation. We currently support 4 PSR-7/ServerRequest creator combinations (Slim-Psr7, Nyholm PSR-7 & Nyholm PSR-7 Server, Guzzle PSR-7 and Guzzle HTTP Factory and Zend-Diactoros.



  • #2642 Added AppFactory to enable PSR-7 implementation and ServerRequest creator auto-detection.
  • #2641 Added RouteCollectorProxyInterface which extracts all the route mapping functionality from app into its own interface.
  • #2640 Added RouteParserInterface and decouple FastRoute route parser entirely from core. The methods relativePathFor(), urlFor() and fullUrlFor() are now located on this interface.
  • #2639 Added DispatcherInterface and decouple FastRoute dispatcher entirely from core. This enables us to swap out our router implementation for any other router.
  • #2638 Added RouteCollector::fullUrlFor() to give the ability to generate fully qualified URLs
  • #2634 Added ability to set invocation strategy on a per-route basis. $app->get(...)->setInvocationStrategy($strategy)
  • #2555 Added PSR-15 Middleware Support
  • #2529 Slim no longer ships with a PSR-7 implementation. You need to provide a PSR-7 ServerRequest and a PSR-17 ResponseFactory to run Slim.
  • #2507 Method names are now case-sensitive in Router::map(), and so, by extension, in App::map()
  • #2497 PSR-15 RequestHandlers can now be used as route callables
  • #2496 A Slim App can now be used as PSR-15 Request Handler
  • #2405 RoutingMiddleware now adds the routingResults request attribute to hold the results of routing
  • #2404 Slim 4 requires PHP 7.1 or higher
  • #2425 Added $app->redirect()
  • #2398 Added Middleware\ErrorMiddleware
  • #2329 Added Middleware\MethodOverrideMiddleware
  • #2288 Separate routing from dispatching
  • #2254 Added Middleware\ContentLengthMiddleware
  • #2166 Added Middleware\OutputBufferingMiddleware


  • #2654 RouteParser::pathFor() and RouteParser::relativePathFor() are deprecated. Use RouteParser::urlFor() and RouteParser::relativeUrlFor()
  • #2641 Deprecate RouteCollector::pushGroup(),RouteCollector::popGroup() which gets replaced by RouteCollector::group()
  • #2638 Deprecate RouteCollector::pathFor() which gets replaced by RouteCollector::urlFor() preserving the orignal functionality
  • #2589 Remove App::$settings
  • #2560 Remove binding of $this to RouteGroup callable.
  • #2555 Double-Pass Middleware Support has been deprecated


  • #2612 Remove Routable, refactored RouteGroup and Route interface
  • #2589 Remove App::$settings altogether
  • #2587 Remove Pimple as a dev-dependency
  • #2398 Slim no longer has error handling built into App. Add Slim\Middleware\ErrorMiddleware as the outermost middleware.
  • #2375 Slim no longer sets the default_mimetype to an empty string, so you need to set it yourself in php.ini or your app using ini_set('default_mimetype', '');.
  • #2288 determineRouteBeforeAppMiddleware setting is removed. Add RoutingMiddleware() where you need it now.
  • #2254 addContentLengthHeader setting is removed
  • #2221 Slim\Http has been removed and Slim now depends on the separate Slim-Http component
  • #2166 outputBuffering setting is removed
  • #2078 Remove App::subRequest()
  • #2098 Remove CallableResolverTrait
  • #2102 Remove container from router
  • #2124 Remove Slim\Exception\SlimException
  • #2174 Switch from Container-Interop to PSR-11
  • #2290 Removed container
  • #2560 Remove binding of $this to group()


  • #2588 Fix file/directory permission handling of Router::setCacheFile()
  • #2067 Unit tests now pass on Windows systems
  • #2405 We rawurldecode() the path before passing to FastRoute, so UTF-8 characters in paths should now work.

Step-By-Step Hello World

Step 1: Install Composer

Don’t have Composer? It’s easy to install by following the instructions on their download page.

Step 2: Install Slim

We recommend you install Slim with Composer. Navigate into your project’s root directory and execute the bash command shown below. This command downloads the Slim Framework and its third-party dependencies into your project’s vendor/ directory.

composer require slim/slim "^4.0"

Step 3: Install a PSR-7 Implementation and ServerRequest Creator

Before you can get up and running with Slim you will need to choose a PSR-7 implementation that best fits your application. In order for auto-detection to work and enable you to use AppFactory::create() and App::run() without having to manually create a ServerRequest you need to install one of the following implementations:

Slim PSR-7

composer require slim/psr7

Nyholm PSR-7 and Nyholm PSR-7 Server

composer require nyholm/psr7 nyholm/psr7-server

Guzzle PSR-7 and Guzzle HTTP Factory

composer require guzzlehttp/psr7 http-interop/http-factory-guzzle

Zend Diactoros

composer require zendframework/zend-diactoros

Step 4: Hello World

use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
use Slim\Factory\AppFactory;

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

$app = AppFactory::create();

$app->get('/', function (Request $request, Response $response, $args) {
    $response->getBody()->write("Hello world!");
    return $response;


Slim 4 DDD Skeleton

@l0gicgate created an app skeleton with a DDD style directory structure, example files and test coverage. It is a very opinionated and we’re not sure yet if it is the right fit for a skeleton but we would like some feedback. You can clone the skeleton and try it out:

git clone
git checkout 4.x