test.php

public function registerAction(Request $request)
{
    $user = new User();
    $form = $this->formFactory->create('user', $user);
    $form->handleRequest($request);
    
    if ($form->isValid()) {
        $this->userManager->save($user);
        
        // ...
    }
    
    return [
        'form' => $form->createView(),
    ];
}