Voir How to Use a Form without a Data Class

use Symfony\Component\Form\Extension\Core\Type\TextType;
use Symfony\Component\Form\Extension\Core\Type\PasswordType;
use Symfony\Component\HttpFoundation\Request;
...
 
class LoginController extends AbstractController {
 
    public function edit(
        Request $request
    ) {
 
        $defaultData = [
            'username' => "coco",
            'password' => "l'asticot",
        ];
 
        $form = $this->createFormBuilder($defaultData)
            ->add('username', TextType::class)
            ->add('password', PasswordType::class)
            ->getForm();
 
        $form->handleRequest($request);
 
        if($form->isSubmitted() && $form->isValid()) {
 
            // Afficher le contenu du formulaire
            dd($form->getData());
 
        }
 
        return $this->render('login/login.html.twig', [
            'my_form' => $form->createView(),
        ]);
    }
}

{{ form_start(my_form) }}
{{ form_widget(my_form) }}
<button type="submit" class="btn btn-primary">Login</button>
{{ form_end(my_form) }}