Untitled

public function agregar(Request $request)
{
    $persona = new Persona();
    $formulario = $this->createForm(PersonaType::class,$persona);
 //   $this->render('base.html.twig',array("persona"=>$formulario->createView()));
    $formulario->handleRequest($request);
    if($formulario -> isSubmitted() && $formulario->isValid())
    {
        $persona = $formulario->getData();

        $db = $this->getDoctrine()->getManager();
        $db->persist($persona);
        $db->flush();

        return new Response('<html>hola </html>');
    }
    else
    {
        return new Response('<html>chau </html>');
    }
}

/**
 * @Route("/post", name="post_list")
 */
public function mostar()
{
    $formulario = $this->createForm(PersonaType::class);
    return $this->render('base.html.twig',array("persona"=>$formulario->createView()));
}

<h2>Formulario con Symfony3</h2>
{{form(persona)}}
{{form_end(persona)}}