pfSense

function unbound_acl_id_used($id) {

	global $config;

	if (is_array($config['installedpackages']['unboundacls']['config']))

		foreach ($config['installedpackages']['unboundacls']['config'] as & $acls)

			if ($id == $acls['aclid'])

				return true;

	return false;

}

function unbound_get_next_id() {

	$aclid = 0;

	while(unbound_acl_id_used($aclid))

		$aclid++;

	return $aclid;

}