$app->get('/content', AppControllersContentController::class);

<?php

namespace AppControllers;

class ContentController
{
    protected $container;

    // Passes the DIC to get the model.
    function __construct($container)
    {
        $this->container = $container;
    }

    function __invoke($request, $response, $args)
    {

        $datas = $this->container->get('contentModel');

        $args['content'] = $datas->testContent();

        // get the template renderer and pass response and datas to the template file.
        return $this->container->get('renderer')->render($response, 'content.php', $args);
    }

<?php

namespace AppModels;

class Model
{
    // Passes the DIC to get db later.
    function __construct($container)
    {
        $this->container = $container;
    }


    protected function executeQuery($sql, $params = null) {
        if ($params == null)
        {
            $result = $this->container->get('db')->query($sql); // direct execution
        } else {
            $result = $this->container->get('db')->prepare($sql); // prepared execution
            $result->execute($params);
        }
        return $result;
    }

}

<?php

namespace AppModels;

Class ContentModel extends Model
{

    public function testContent()
    {
        $testDatas = "Hello world";
        return $testDatas;
    }

    public function getContent()
    {
        $sql = 'SELECT * FROM posts';
        $posts = $this->executeQuery($sql);
        return $posts;
    }


}

<?php

use SlimApp;

return function (App $app) {
$container = $app->getContainer();

// View renderer
$container['renderer'] = function ($c) {
    $settings = $c->get('settings')['renderer'];
    return new SlimViewsPhpRenderer($settings['template_path']);
};

// Database
$container['db'] = function ($c) {
    $db = $c['settings']['db'];
    $pdo = new PDO('mysql:host=' . $db['host'] . ';dbname=' . $db['dbname'],
        $db['user'], $db['pass']);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    $pdo->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
    return $pdo;
};


// Model data stored
$container['contentModel'] = new AppModelsContentModel();

};