This option determines what value the field will *return* when the submittedvalue is empty (or missing). It does not set an initial value if none isprovided when the form is rendered in a view.This means it helps you handling form submission with blank fields. Forexample, if you want the ``name`` field to be explicitly set to ``John Doe``when no value is selected, you can do it like this::    $builder->add('name', null, [        'required'   => false,        'empty_data' => 'John Doe',    ]);This will still render an empty text box, but upon submission the ``John Doe``value will be set. Use the ``data`` or ``placeholder`` options to show thisinitial value in the rendered form.If a form is compound, you can set ``empty_data`` as an array, object orclosure. See the :doc:`/form/use_empty_data` article for more details aboutthese options... note::    If you want to set the ``empty_data`` option for your entire form class,    see the :doc:`/form/use_empty_data` article.--.. caution::--    :doc:`Form data transformers </form/data_transformers>` will still be-    applied to the ``empty_data`` value. This means that an empty string will-    be cast to ``null``. Use a custom data transformer if you explicitly want-    to return the empty string.