ActivityType

<?php

namespace Newism\ActivityBundle\Form;

use Symfony\Component\Form\AbstractType,
    Symfony\Component\Form\FormBuilder,
    Symfony\Component\Form\FormEvents,
    Symfony\Component\Form\Event\DataEvent;

use Newism\ProjectBundle\Form\EventListener\AddTaskFieldSubscriber;

class ActivityType extends AbstractType
{
    public function buildForm(FormBuilder $builder, array $options)
    {
         $builder
            ->add('description')
            ->add('duration')
            ->add('timerStartedAt')
            ->add('startedAt')
            ->add('user')
        ;
    }

    public function getName()
    {
        return 'newism_activitybundle_activitytype';
    }
}

gistfile1.txt

    <form 
        action="{{ path('put_activity', {'id': activity.object.id }) }}" 
        method="post"
        {{ form_enctype(activity.edit_activity_form) }}
    >
        <input type="hidden" name="_method" value="PUT" />
        <input type="hidden" name="_target_path" value="get_activities" />
        {{ form_errors(activity.edit_activity_form) }}
        {{ form_widget(activity.edit_activity_form._token) }}
        <div class="ft ft-textarea ft-description">
            <label>
                {{ form_label(create_activity_form.description) }}
            </label>
            {{ form_widget(create_activity_form.description) }}
        </div>
        <div class="actions">
            <button type="submit">Edit Activity</button>
        </div>
    </form>

putActivityAction

<?php
    /**
     * Updates an existing Activity entity.
     * @Route("/activity/{id}", name="put_activity")
     * @Method("put")
     */
    public function putActivityAction($id)
    {
        $em = $this->getDoctrine()->getEntityManager();
        $activity = $em->getRepository('Newism\ActivityBundle\Entity\Activity')->find($id);
        if (!$activity) {
            throw $this->createNotFoundException('Unable to find Activity entity.');
        }
        $activity = $em->getRepository('Newism\ActivityBundle\Entity\Activity')->find($id);
        $editForm   = $this->createForm(new ActivityType(), $activity);
        $request = $this->getRequest();
        $editForm->bindRequest($request);


        if ($editForm->isValid()) {
            $em->persist($activity);
            $em->flush();
        }

        if(!$target_path = $this->getRequest()->request->get('_target_path')) {
            $target_path = "get_activities";
        }

        return $this->redirect($this->generateUrl($target_path, array('id' => $activity->getId())));
    }