在SLIM框架中创建全局变量以用于其他路由

如何解决在SLIM框架中创建全局变量以用于其他路由

我需要创建一个全局变量以用于其他途径，我不熟悉SLIM框架，而且我搜索的所有内容都无法正常工作。
因此，基本上我会在显示主屏幕的路线中获取价格，然后在创建STRIPE API会话的另一条路线中使用该价格。见下文;

$app = new Slim\App;

$app->get('/pay/{price}',function (Request $request,Response $response,$args) {
  $response->getBody()->write(file_get_contents("../../client/index.html"));
  $key = "8881727727272";
  $decrypted = openssl_decrypt(hex2bin($args['price']),'AES-128-CBC',$key); <---- CREATED HERE!!!
  return $response;
});
$app->get('/success',$args) {
  $response->getBody()->write(file_get_contents("../../client/success.html"));
  return $response;
});
$app->get('/cancel',$args) {
  $response->getBody()->write(file_get_contents("../../client/cancel.html"));
  return $response;
});

$app->post('/create-session',function(Request $request,Response $response) use ($app)  {
  try {
    $cafe = 'test';
    $session = \Stripe\Checkout\Session::create([
      'payment_method_types' => ['card'],'line_items' => [[
        'name' => $cafe,'description' => 'ordering','images' => [''],'amount' => $decrypted,<--- Needs to be used again here!
        'currency' => 'aud','quantity' => 1,]],'success_url' => 'http://localhost/success?session_id={CHECKOUT_SESSION_ID}','cancel_url' => 'http://localhost/cancel',]);
    createSession($session->id);
  } catch (Exception $e) {
    return $response->withJson($e->getJsonBody(),400);
  }
  return $response->withJson($session);
});

如果有人有什么好主意！谢谢