// Success notification
flash('Your changes have been saved!');

// In controller
public function save(): Response
{
    // Your logic...

    flash('Operation completed successfully!');

    return $this->redirectToRoute('home');
}

// With dependency injection
public function save(FlasherInterface $flasher): Response
{
    // Your logic...

    $flasher->success('Changes saved!');

    return $this->redirectToRoute('home');
}