What is Dependency Container in Slim Framework?

Slim Framework - Interview Questions

Slim uses an optional dependency container to prepare, manage, and inject application dependencies. Slim supports containers that implement PSR-11 like PHP-DI.

Example usage with PHP-DI : You don’t have to provide a dependency container. If you do, however, you must provide an instance of the container to AppFactory before creating an App.

<?php
use DI\Container;
use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;
use Slim\Factory\AppFactory;

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

// Create Container using PHP-DI
$container = new Container();

// Set container to create App with on AppFactory
AppFactory::setContainer($container);
$app = AppFactory::create();

Add a service to your container :

$container->set('myService', function () {
    $settings = [...];
    return new MyService($settings);
});

You can fetch services from your container explicitly as well as from inside a Slim application route like this:

/**
 * Example GET route
 *
 * @param  ServerRequestInterface $request  PSR-7 request
 * @param  ResponseInterface      $response  PSR-7 response
 * @param  array                  $args Route parameters
 *
 * @return ResponseInterface
 */
$app->get('/foo', function (Request $request, Response $response, $args) {
    $myService = $this->get('myService');

    // ...do something with $myService...

    return $response;
});

To test if a service exists in the container before using it, use the has() method, like this:

/**
 * Example GET route
 *
 * @param  ServerRequestInterface $request  PSR-7 request
 * @param  ResponseInterface      $response  PSR-7 response
 * @param  array                  $args Route parameters
 *
 * @return ResponseInterface
 */
$app->get('/foo', function (Request $request, Response $response, $args) {
    if ($this->has('myService')) {
        $myService = $this->get('myService');
    }
    return $response;
});