Originally I wanted to display radio buttons without the possibility of changing them.
I tried using the read_only attribute on my field type first:

$builder->add('onCall', 'choice', array(
    'choices' => array(0 => 'no', 1 => 'yes'),
    'expanded' => true,
    'read_only' => true
));

As expected the readonly attribute gets added to the input:

<input id="timekeeping_entry_day_onCall_0" type="radio" value="0" required="required" readonly="readonly" name="timekeeping_entry_day[onCall]">

But in the end this does not have any effect since - as we all know by now - readonly is not supported for radio buttons:
http://www.w3.org/TR/WD-forms-970402#readonly
READONLY applies to INPUT elements of type TEXT or PASSWORD and to the TEXTAREA element.

So allowing the read_only option on an expanded choice does not seem to make sense anyway, correct?

The desired effect on the element should be to disable it. But setting disabled on the field type will ignore validation after form submit if the radio buttons have been enabled again by a javascript on client side.

So it looks like the only way to do it is to set the HTML attribute disabled on the field type.
This way it can be enabled again by the client and the submitted value would not be ignored.

My attempt for this:

$builder->add('onCall', 'choice', array(
    'choices' => array(0 => 'no', 1 => 'yes'),
    'expanded' => true,
    'attr' => array('disabled' => 'disabled')
));

Unfortunately the HTML result does not apply the disabled attribute to the input but to the div around it:

<div id="timekeeping_entry_day_onCall" disabled="disabled">
<input id="timekeeping_entry_day_onCall_0" type="radio" value="0" required="required" name="timekeeping_entry_day[onCall]">
<label class="required" for="timekeeping_entry_day_onCall_0">no</label>
<input id="timekeeping_entry_day_onCall_1" type="radio" value="1" required="required" name="timekeeping_entry_day[onCall]">
<label class="required" for="timekeeping_entry_day_onCall_1">yes</label>
</div>

I'm not using the Bootstrap theme.

Setting the attr seems to be the issue:

• [Form] Radio choice form builder does not render attr #8269 by @sargath
• radio choice form builder does not render attr #8051 by @AdamQuadmon

The div uses the widget_container_attributes block:
https://github.com/symfony/symfony/blob/2.7/src/Symfony/Bridge/Twig/Resources/views/Form/form_div_layout.html.twig#L46

While the input uses a widget_attributes block:
https://github.com/symfony/symfony/blob/2.7/src/Symfony/Bridge/Twig/Resources/views/Form/form_div_layout.html.twig#L93

Are the attr passed to the wrong block?

Original issue I started:

• Form field type 'sonata_type_translatable_choice' cannot be used readonly or disabled sonata-project/SonataAdminBundle#2842

Possibly related:

• form field type option disabled should not ignore submitted value #12946