How do I add an unbound field to a form in Symfony which is otherwise bound to an entity?

Question

Maybe I'm missing the obvious but how do I (or can I) add an extra "unbound" field to a Symfony form that is otherwise bound to an entity?

Let's say I have an entity with fields first_name and last_name. I do the typical thing in my form class buildForm method.

$builder
    ->add('first_name')
    ->add('last_name')
;

and this in my controller:

$editForm = $this->createForm(new MyType(), $entity);

That works nicely but I'd like to add another text box, let's call it "extra", and receive the value in the POST action. If I do $builder->add('extra')‍, it complains that

NoSuchPropertyException in PropertyAccessor.php line 479:

Neither the property "extra" nor one of the methods "getExtra()", "extra()", "isExtra()", "hasExtra()", "__get()" exist and have public access in class...

Which is correct. I just want to use it to collect some extra info from the user and do something with it other than storing it with the entity.

I know how to make a completely standalone form but not one that's "mixed". Is this possible?

Answer 1

In your form add a text field with a false property_path:

$builder->add('extra', 'text', array('property_path' => false));

You can then access the data in your controller:

$extra = $form->get('extra')->getData();

UPDATE

The new way since Symfony 2.1 is to use the mapped option and set that to false.

->add('extra', null, array('mapped' => false))

Credits for the update info to Henrik Bjørnskov ( comment below )