**type**: ``string`` or ``Boolean``

.. versionadded:: 2.3

Since Symfony 2.3, empty values are also supported if the ``expanded``

option is set to true.

This option determines whether or not a special "empty" option (e.g. "Choose an option")

will appear at the top of a select widget. This option only applies ifboth

the ``expanded`` and ``multiple``options are set to false.

will appear at the top of a select widget. This option only applies ifthe

the ``multiple``option is set to false.

* Add an empty value with "Choose an option" as the text::

// a blank (with no text) option will be added

$builder->add('states', 'choice', array(

'required' => false,

));

));