This package configures Slim to work with the PHP-DI container.

The full documentation is here: http://php-di.org/doc/frameworks/slim.html

The most obvious difference with the default Slim installation is that you will be using PHP-DI as the container, which has the following benefits:

• autowiring
• powerful configuration format
• support for modular systems
• ...

If you want to learn more about all that PHP-DI can offer have a look at its introduction.

While your controllers can be simple closures, you can also write them as classes and have PHP-DI instantiate them only when they are called:

class UserController
{
    private $userRepository;
    
    public function __construct(UserRepository $userRepository)
    {
        $this->userRepository = $userRepository;
    }

    public function delete($request, $response)
    {
        $this->userRepository->remove($request->getAttribute('id'));
        
        $response->getBody()->write('User deleted');
        return $response;
    }
}

$app->delete('/user/{id}', ['UserController', 'delete']);

Dependencies can then be injected in your controller using autowiring, PHP-DI config files or even annotations.

By default, Slim controllers have a strict signature: $request, $response, $args. The PHP-DI bridge offers a more flexible and developer friendly alternative.

Controller parameters can be any of these things:

• the request or response (parameters must be named $request or $response)
• route placeholders
• request attributes
• services (injected by type-hint)

You can mix all these types of parameters together too. They will be matched by priority in the order of the list above.

You can inject the request or response in the controller parameters by name:

$app->get('/', function (ResponseInterface $response, ServerRequestInterface $request) {
    // ...
});

As you can see, the order of the parameters doesn't matter. That allows to skip injecting the $request if it's not needed for example.

$app->get('/hello/{name}', function ($name, ResponseInterface $response) {
    $response->getBody()->write('Hello ' . $name);
    return $response;
});

As you can see above, the route's URL contains a name placeholder. By simply adding a parameter with the same name to the controller, PHP-DI will directly inject it.

$app->add(function (ServerRequestInterface $request, RequestHandlerInterface $handler) {
    $request = $request->withAttribute('name', 'Bob');
    $response = $handler->handle($request);
    return $response;
});

$app->get('/', function ($name, ResponseInterface $response) {
    $response->getBody()->write('Hello ' . $name);
    return $response;
});

As you can see above, a middleware sets a name attribute. By simply adding a parameter with the same name to the controller, PHP-DI will directly inject it.

To inject services into your controllers, you can write them as classes. But if you want to write a micro-application using closures, you don't have to give up dependency injection either.

You can inject services by type-hinting them:

$app->get('/', function (ResponseInterface $response, Twig $twig) {
    return $twig->render($response, 'home.twig');
});

Note: you can only inject services that you can type-hint and that PHP-DI can provide. Type-hint injection is simple, it simply injects the result of $container->get(/* the type-hinted class */).

The documentation can be read here: http://php-di.org/doc/frameworks/slim.html