обработчик формы авторизации

function login() {
  if(isset($POST['username']) && isset($POST['password'])) {
    $username = $_POST['username'];
    $password = $_POST['password'];
    $user = $this->loginService->getUserByUsername($username);
    if($user && $this->loginService->checkPassword($password, $user->getPasswordHash())) {
      $this->loginService->login($user);
    }
  }
}