Populate a Symfony 2 Form with the referring entity

In any web project it often happens that you have an entity, say a Group, to which you want to add a linked entity, say a Student. So you’ll have a “Add a Student” link on the page displaying the Group. When your users click through, there’s probably a dropdown with the different groups, and your users expect the Group they’re coming from to be prepopulated.

There’s various ways to do this, but I’d like to show you a simple, non intrusive one for Symfony 2. You don’t have to add any parameters to the link, it just works. In your Student Controller, the newAction method:

  <?php
  // src/My/Bundle/Controller/StudentController.php
      public function newAction()
      {
          $entity = new Student();
          $form   = $this->createForm(new StudentType(), $entity);
  
          // Get the refering URL Path
          $ref = str_replace("app_dev.php/", "", parse_url($request->headers->get('referer'),PHP_URL_PATH ));
          // Get the matching route
          $route = $this->container->get('router')->match($ref);
          if (empty($route['_route']) === false && $route['_route'] === 'group_show') {
              // Find the referring group
              if ($group = $this->get('doctrine')->getRepository('MyBundle:Group')->findOneById($route['id'])) {
                  $form->get('group')->setData($group);
              }
          }
  
          return $this->render('MyBundle:Student:new.html.twig', array(
              'entity' => $entity,
              'form'   => $form->createView(),
          ));
      }
  ?>
  

We basically try and match the referring URL to a route, and if found, retrieve that entity, and set it in the form. Simple!