What might cause the PHP Uncaught Error: Using $this when not in object context error?

Question

PHP

Good afternoon, I'm writing my own "framework" (I call it that for myself, but in fact it's just self-written garbage, I just write purely for myself to practice). And I ran into a problem that I can not understand.
I have class App. which is the parent of custom classes and methods, it looks like this

<?php
namespace App;
use Symfony\Component\Yaml\Yaml;
define('BASE_DIR', __DIR__ . '/../');
class App
{
    /**
     * @var Router
     */
    public $router;

    /**
     * App constructor.
     */
    public function __construct()
    {
        $this->router = new Router();
    }

    public final function run(){
        $this->router->match();
    }

    /**
     * @param string $view
     * @param array|null $parameters
     * @return string
     * @throws \Twig_Error_Loader
     * @throws \Twig_Error_Runtime
     * @throws \Twig_Error_Syntax
     */
    public function render(string $view, array $parameters = null) {
        $twig = new Twig();
        return $twig->render($view, $parameters);
    }

    /**
     * @param string $parameter
     * @return mixed
     */
    public function getParameter(string $parameter) {
        $file = Yaml::parseFile(BASE_DIR . 'config/config.yml');
        $parameters = $file['parameters'];
        return $parameters[$parameter];
    }
}

I also have my custom class, which is called when going to the main page

<?php
namespace Controller;
use App\App;
class AppController extends App
{

    public function indexAction() {
        return $this->render('index.twig', [
            'foo' => 'bar'
        ]);
    }
}

and as you may have guessed from the question, I get Fatal error Uncaught Error: Using $this when not in object context in /var/www/html/framework/src/Controller/AppController in line 12 ( when calling $this->render () )
What could be the problem, because I'm just inheriting a class that doesn't have any static methods or properties?

Answer 1

You are calling the indexAction method statically. You must first create an AppController object on which to call it