Problems with differences between Slim v2.6 and current 3.2

I had this problem as well. It would be great if they did an updated version of this course with the new Slim 3.x features.

In composer, I believe you are able to specify the version that you would like to install for Slim. Try removing your current Slim install, and then install its previous version to follow along in the tutorials. Not the optimal solution as you are using an outdated version of Slim, but in order to complete the challenges etc it might be the only way for now.

I feel ya. I am pulling my hair out trying to follow this tutorial and trying to search for answers on google for Slim 3. Why would I downgrade to v2 if I'm eventually gonna have to learn v3?

I had the same problem that you had with the Slim v2 vs. v3. Anyway, after reading about some of the differences between the 2 versions, and lots of troubleshooting, the following code worked for me (I left out the monolog library for simplicity). It's pretty much from the slimframework website, although I had to change the templates directory to match the instructions from the speaker.

require '/vendor/autoload.php';

$app = new \Slim\App();

// Get container
$container = $app->getContainer();

// Register component on container
$container['view'] = function ($container) {
    $view = new \Slim\Views\Twig("templates/", [
        'cache' => false
    ]);
    $view->addExtension(new \Slim\Views\TwigExtension(
        $container['router'],
        $container['request']->getUri()
    ));

    return $view;
};

$app->get('/', function ($request, $response, $args) {
    return $this->view->render($response, "about.twig");
})->setName('profile');

$app->get('/contact', function ($request, $response, $args) {
    return $this->view->render($response, "contact.twig");
})->setName('profile');

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

I followed Steven's steps to finish it with Slim v3. Thanks, Steven.