Helper::isAdmin

static function isAdmin(int $userId): bool
{
	global $USER;
	if ($userId === $USER->GetID() && $USER->isAdmin())
	{
		return true;
	}

	if (BitrixMainLoader::includeModule('bitrix24'))
	{
		return CBitrix24::IsPortalAdmin($userId);
	}

	$groups = CUser::GetUserGroup($userId);
	$groups = array_map('intval', $groups);
	return in_array(1, $groups, true);
}