pfSense

/* sort by interface only, retain the original order of rules that apply to

   the same interface */

function filter_rules_sort() {

	global $config;

	/* mark each rule with the sequence number (to retain the order while sorting) */

	for ($i = 0; isset($config['filter']['rule'][$i]); $i++)

		$config['filter']['rule'][$i]['seq'] = $i;

	usort($config['filter']['rule'], "filter_rules_compare");

	/* strip the sequence numbers again */

	for ($i = 0; isset($config['filter']['rule'][$i]); $i++)

		unset($config['filter']['rule'][$i]['seq']);

}

function filter_rules_compare($a, $b) {

	if ($a['interface'] == $b['interface'] || ( isset($a['floating']) && isset($b['floating']) ))

		return $a['seq'] - $b['seq'];

	else if (isset($a['floating']))

		return -1;

	else if (isset($b['floating']))

		return 1;

	else

		return compare_interface_friendly_names($a['interface'], $b['interface']);

}