PHP-DI does not inject the required class

I am using php-di in according to do dependency injection. The requests first arrive in the route.php file which configures php-di (for example to use AccountService when IAccountService is required) and then the container is asked to create appropriate controller. The source code of route.php is as following:

<?php
  spl_autoload_register(function ($class_name) {
    switch ($class_name){
      case 'AccountController':
        require_once 'controllers/account_controller.php';
        break;
      case 'AccountService':
      case 'IAccountService':
        require_once 'services/account_service.php';
        break;
      case 'URLHELPER':
        require_once 'helpers/URLHELPER.php';
        break;
      case 'STRINGHELPER':
        require_once 'helpers/STRINGHELPER.php';
        break;
      case 'STRINGHELPER':
        require_once "helpers/HASHHELPER.php";
        break;
    }
  });

  function call($controller, $action) {
    $container = DI\ContainerBuilder::buildDevContainer();
    $container->set('IAccountService', \DI\object('AccountService'));

    // require the file that matches the controller name
    require_once('controllers/' . $controller . '_controller.php');

    // create a new instance of the needed controller
    switch($controller) {
      case 'home':
        $controller = $container->get('HomeController');
      case 'account':
        $controller = $container->get('AccountController');
      break;
    }

    // call the action
    $controller->{ $action }();
  }

  // just a list of the controllers we have and their actions
  // we consider those "allowed" values
  $controllers = array(
    'home' => ['index', 'error']
    ,'account' => ['login']
  );

  // check that the requested controller and action are both allowed
  // if someone tries to access something else he will be redirected to the error action of the pages controller
  if (array_key_exists($controller, $controllers)) {
    if (in_array($action, $controllers[$controller])) {
      call($controller, $action);
    } else {
      call('home', 'error');
    }
  } else {
    call('home', 'error');
  }
?>

now mention this line $controller = $container->get('AccountController'); Where AccountController is selected. After this I got the error.

The source code of AccountController:

<?php
  class AccountController {

    private $accountService;

    public function __construct(IAccountService $accountService) {
        echo $accountService == null;
        $this->accountService = $accountService;
    }

    public function login() {
        if(isset($_POST) && isset($_POST["email"]) && isset($_POST["password"])){
            $loginResult = $this->$accountService->login($_POST["email"], $_POST["password"]);
            if($loginResult){
                $this->URLHELPER::redirectToAction("home", "index");
                die;
            }
            else{
                echo "Oops! this Email and Password combination not found";
            }
        }
        require_once('views/account/login.php');
    }
  }
?>

It seems that DI does not inject the AccountService and the error is as following:

Notice: Undefined variable: accountService in /opt/lampp/htdocs/UMTest/controllers/account_controller.php on line 13

Notice: Undefined property: AccountController::$ in /opt/lampp/htdocs/UMTest/controllers/account_controller.php on line 13

Fatal error: Uncaught Error: Call to a member function login() on null in /opt/lampp/htdocs/UMTest/controllers/account_controller.php:13 Stack trace: #0 /opt/lampp/htdocs/UMTest/routes.php(40): AccountController->login() #1 /opt/lampp/htdocs/UMTest/routes.php(54): call(Object(AccountController), 'login') #2 /opt/lampp/htdocs/UMTest/views/layout.php(10): require_once('/opt/lampp/htdo...') #3 /opt/lampp/htdocs/UMTest/index.php(36): require_once('/opt/lampp/htdo...') #4 {main} thrown in /opt/lampp/htdocs/UMTest/controllers/account_controller.php on line 13

Where is my mistake?

For accessing property you have to use $this->accountService not $this->$accountService change following line in login()

$loginResult = $this->$accountService->login($_POST["email"], $_POST["password"]);

to

$loginResult = $this->accountService->login($_POST["email"], $_POST["password"]);