Action classes

While handlers are functions inside config/routes.php, the file grows with every route. A handler is moved into a separate class — an action. One class is responsible for one route, and the routes file keeps a single line.

Where actions live

Actions go into the src/Action/ folder. Slim has no command to create them: make the folder and the file by hand.

The first action

// src/Action/HomeAction.php
namespace App\Action;
 
use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
 
final class HomeAction
{
    public function __invoke(Request $request, Response $response): Response
    {
        $response->getBody()->write('Blog home page');
 
        return $response;
    }
}

__invoke is a special PHP method: an object that has it can be called like a function. The arguments are the same as for a handler function.

Using it in a route

In config/routes.php the class name replaces the function:

// config/routes.php
use App\Action\HomeAction;
use Slim\App;
 
return function (App $app): void {
    $app->get('/', HomeAction::class)->setName('home');
};

Open http://localhost:8080 — the page is the same, but the handler code now has its own file. Slim creates the class object itself when a request arrives.

An action with a placeholder

Placeholders arrive as the third argument, just as in a function:

// src/Action/ShowPostAction.php
namespace App\Action;
 
use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
 
final class ShowPostAction
{
    public function __invoke(Request $request, Response $response, array $args): Response
    {
        $response->getBody()->write('Post #' . (int) $args['id']);
 
        return $response;
    }
}

// config/routes.php
$app->get('/posts/{id:[0-9]+}', ShowPostAction::class)->setName('posts.show');

The address /posts/5 prints "Post #5". Remember to add use App\Action\ShowPostAction; at the top of the routes file.

Naming

An action name answers the question "what does the route do":

A controller instead of actions

If a controller — one class with several methods — feels more familiar, the route is written as an array of the class name and the method name:

// config/routes.php
$app->get('/posts', [PostController::class, 'index']);
$app->get('/posts/{id:[0-9]+}', [PostController::class, 'show']);

The index and show methods take the same arguments as __invoke. The course uses actions: each class is short and receives only what its route needs.

Common mistake

An action that parses the request, runs database queries and builds HTML all by itself turns into a "fat" class. Keep three steps in an action: take data from the request, call another class that does the work, and build the response. How to pass such classes into an action is shown in the next lesson.