How to get the value of select in a controller?

I work with a Page entity (to manage a list a page...)

I have a entity Field Type :

$builder
     ->add('parent', 'entity', array(
           'class' => 'EliophotBackBundle:Page',
           'query_builder' => function(EntityRepository $er) {
                 return $er->createQueryBuilder('p')
                     ->join('p.translations', 'pt')
                     ->where('p.id = pt.translatable')
                     ->andWhere('pt.locale = :lang')
                     ->setParameter('lang', 'fr')
                  ;
            },
         'label' => 'Page parente ?',
         'multiple' => false,
         'required' => false,
         'empty_value' => 'Choisissez une page parente',
         'empty_data'  => null,

));

and I have a __toString method in my Page entity to display the page name into the select field :

public function __toString() 
{
    return (string) $this->getName();
}

So in my twig template I have a select field that displays the list of the page like this :

<select>
<option value="1">page 1</option>
<option value="2">page 2</option>
<option value="3">page 3</option>
...
</select>

But when I submit the form, I only get the value of the select choiced, "page 1" for example.

But I want to stored the id present in the value in my database, not the string... So how can I get the value of the select in my controller ?

I try this but it only return the name of the page selected :

$myForm->get('parent')->getData(); //dump = 'page 1' for example