An entity-bound allowed values callback.
function list_test_dynamic_values_callback($field, $instance, $entity_type, $entity, &$cacheable) {
$cacheable = FALSE;
// We need the values of the entity as keys.
return drupal_map_assoc(array_merge(array(
$entity->ftlabel,
), entity_extract_ids($entity_type, $entity)));
}