CIBlockDocument::GetUsersFromUserGroup

static function GetUsersFromUserGroup($group, $documentId)
{
	$group = mb_strtolower($group);
	if ($group == 'author')
	{
		$documentId = (int)$documentId;
		if ($documentId <= 0)
			return array();

		$db = CIBlockElement::GetList(array(), array("ID" => $documentId, "SHOW_NEW" => "Y", "SHOW_HISTORY" => "Y"), false, false, array("ID", "IBLOCK_ID", "CREATED_BY"));
		if ($ar = $db->Fetch())
			return array($ar["CREATED_BY"]);
		return array();
	}

	if ((string)intval($group) !== (string)$group)
		return array();

	$group = (int)$group;
	if ($group <= 0)
		return array();

	$arResult = array();

	$arFilter = ['ACTIVE' => 'Y', 'IS_REAL_USER' => true];
	if ($group != 2)
	{
		$arFilter["GROUPS_ID"] = $group;
	}

	$dbUsersList = CUser::GetList("ID", "ASC", $arFilter, ['FIELDS' => ['ID']]);
	while ($arUser = $dbUsersList->Fetch())
	{
		$arResult[] = $arUser["ID"];
	}

	return $arResult;
}