symfony get previous url code example

Example: get previous url symfony 4 in formpage

/* in form */
<input type="hidden" name="referer" 
	value="{{app.request.headers.get('referer')}}"/>

/* in controller */
if ($form->isSubmitted() && $form->isValid()) {
    $em->persist($thisEntity);
    $em->flush();
    return $this->redirect($request->request->get('referer'));
}