I’m getting a “class not found” error trying to make a Router work:

GET / - Uncaught Error: Class "AppRouter" not found in /home/zumb/Documents/HHsite/ALPHA_VERSION/public/index.php:4
Stack trace:
#0 {main}
  thrown in /home/zumb/Documents/HHsite/ALPHA_VERSION/public/index.php on line 4

I don’t understand why it can’t find my class.

My folders :

public
-index.php
src
-Router.php
vendor
-altorouter
-composer
-autoload.php
views
tableau.php
composer.json
composer.lock
index.php :

<?php
require '../vendor/autoload.php';

$router = new AppRouter(dirname(__DIR__) . DIRECTORY_SEPARATOR . 'views');
$router
    ->get('', 'tableau', '')
    ->get('/blog/category', 'category/show', 'category')
    ->run();

Router.php :

<?php
namespace App;

class Router {

    /**
     * @var string
     */
    private $viewPath;

    /**
     * @var AltoRouter
     */
    private $router;

    public function __construct(string $viewPath)
    {
        $this->viewPath =  $viewPath;
        $this->router = new AltoRouter();
    }

    public function get(string $url, string $view, ?string $name = null)
    {
        $this->router->map('GET', $url, $view, $name);
        return $this;
    }

    public function run()
    {
        print "hey";
        $match = $this->router->match();
        $view = $match['target'];
        ob_start();
        require $this->viewPath . DIRECTORY_SEPARATOR . $view . '.php';
        $content = ob_get_clean();
        require $this->viewPath . DIRECTORY_SEPARATOR . 'layouts/default.php';

        return $this;
    }
}

composer.json :

{
    "autoload": {
        "psr-4": {
            "App\": "src/"
        }
    },
    "require": {
        "altorouter/altorouter": "^2.0"
    }
}

autoload.php :

<?php

// autoload.php @generated by Composer

if (PHP_VERSION_ID < 50600) {
    if (!headers_sent()) {
        header('HTTP/1.1 500 Internal Server Error');
    }
    $err = 'Composer 2.3.0 dropped support for autoloading on PHP <5.6 and you are running '.PHP_VERSION.', please upgrade PHP or use Composer 2.2 LTS via "composer self-update --2.2". Aborting.'.PHP_EOL;
    if (!ini_get('display_errors')) {
        if (PHP_SAPI === 'cli' || PHP_SAPI === 'phpdbg') {
            fwrite(STDERR, $err);
        } elseif (!headers_sent()) {
            echo $err;
        }
    }
    trigger_error(
        $err,
        E_USER_ERROR
    );
}

require_once __DIR__ . '/composer/autoload_real.php';

return ComposerAutoloaderInitcdc540639fbf1cb4b940a9197d9773c3::getLoader();

I tried “composer dump-autoload”.
It works if I just “require” and “use”.

How can I fix this?