When rendering form type radios using drupal_get_form, each one of the radio's options can be exclusively selected, as the html name attribute is set to the parent's ('radios') id.
However I'm working on an ajax form module that integrates with mailchimp, and renders these form elements individually in isolation using drupal_render so they can be placed in a template.
My code to render radios is as follows:
$form_child = array ( '#title' => 'Some Radios', '#weight' => '6', '#required' => false, '#default_value' => '', '#type' => 'radios', '#options' => array ( 'Option 1' => 'Option 1', 'Option 2' => 'Option 2', 'Option 3' => 'Option 3', ), ); // This is generated in my module $form_child = form_process_radios($form_child); $myhtml = drupal_render($form_child);
And here is what happens on my form: HTML output