Dependencies in Slim Framework

Foo.php

<?php
namespace App;

class Foo
{
    protected $db;
    
    public function __construct(PDO $db)
    {
        $this->db = $db;
    }

    public function doSomething()
    {
        // use $this->db to do something
    }
}

HomeAction.php

<?php
namespace App;

class HomeAction
{
    protected $foo;

    public function __construct(Foo $foo)
    {
        $this->db = $foo;
    }

    public function __invoke($request, $response, $args)
    {
        // do something with $this->foo
        return $reponse;
    }
}

index.php

<?php
$app = new Slim\App(['settings' => ['displayErrorDetails' => true]]);

// set up DIC
$container = new $app->getContainer();

$container['db'] = function ($c) {
    return new PDO();
};

$container[App\Foo::class] = function ($c) {
    return new App\Foo($c->get('db'));
};

$container[App\HomeAction::class] = function ($c) {
    return new App\HomeAction($c->get(App\Foo::class));
};

// register routes
$app->get('/', App\HomeAction::class);

// run application
$app->run();