<?php
function test_settings() {

	$form['fields1'] = array('#type' => 'fieldset', '#tree' => TRUE);

	$form['fields1']['test'] = array(
	'#type' => 'textfield',
	'#title' => t('test'), '#default_value' => 'meow');

	$form['fields1']['format1'] = filter_form(1, 0, array('format1'));

	$form['fields1']['fields2'] = array('#type' => 'fieldset','#tree' => TRUE);
	$form['fields1']['fields2']['test2'] = array(
	'#type' => 'textfield',
	'#title' => t('test2'),
	'#default_value' => 'blah');
	$form['fields1']['fields2']['format2'] = filter_form(2, 0, array('format2'));

	$form['#validate'] = array('test_validate' => array());

	return $form;
}

function test_validate($id, $vars) {
dprint_r($vars);
exit;
}

?>