Submit handler for field_test_entity_nested_form().
function field_test_entity_nested_form_submit($form, &$form_state) {
$entity_1 = entity_create('test_entity', $form_state['values']);
field_attach_extract_form_values($entity_1, $form, $form_state);
field_test_entity_save($entity_1);
$entity_2 = entity_create('test_entity', $form_state['values']['entity_2']);
field_attach_extract_form_values($entity_2, $form['entity_2'], $form_state);
field_test_entity_save($entity_2);
drupal_set_message(t('test_entities @id_1 and @id_2 have been updated.', array(
'@id_1' => $entity_1->ftid,
'@id_2' => $entity_2->ftid,
)));
}