use Symfony\Component\Form\FormInterface; // Check if a form has been submitted if ($form instanceof FormInterface && $form->isSubmitted()) { // Process form data }In this example, the isSubmitted method is called on a FormInterface object named `$form`. If the method returns true, the application will proceed to process the form data. The Symfony\Component\Form namespace contains the FormInterface component, which is part of the Symfony Form library.