How do you default to the empty_value choice in a custom symfony form field type?

Question

I have a created a custom form field dropdown list for filtering by year. One of the things I want to do is to allow the user to filter by all years, which is the default option. I am adding this as an empty_value. However, when I render the form, it defaults on the first item that's not the empty value. The empty value is there, just above it in the list. How do I make the page default to, in my case 'All' when the page initially loads? Code is below.

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilder;

class YearType extends AbstractType
{

  private $yearChoices;

  public function __construct()
  {
      $thisYear = date('Y');
      $startYear = '2012';

      $this->yearChoices = range($thisYear, $startYear);
  }

  public function getDefaultOptions(array $options)
  {
    return array(
        'empty_value' => 'All',
        'choices' => $this->yearChoices,
    );
  }

  public function getParent(array $options)
  {
    return 'choice';
  }

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

I'm rendering my form in twig with a simple {{ form_widget(filter_form) }}

Answer 1

Try adding empty_data option to null, so it comes first. I have many fields of this type and it's working, for example:

class GenderType extends \Symfony\Component\Form\AbstractType
{

    public function getDefaultOptions(array $options)
    {
        return array(
            'empty_data'  => null,
            'empty_value' => "Non specificato",
            'choices'     => array('m' => 'Uomo', 'f' => 'Donna'),
            'required'    => false,
        );
    }

    public function getParent(array $options) { return 'choice'; }

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

}

EDIT: Another possibility (i suppose) would be setting preferred_choices. This way you'll get "All" option to the top. But i don't know if it can work with null empty_data, but you can change empty_data to whatever you want:

  public function getDefaultOptions(array $options)
  {
    return array(
        'empty_value'       => 'All',
        'empty_data'        => null,
        'choices'           => $this->yearChoices,
        'preferred_choices' => array(null)         // Match empty_data
    );
  }