Helper::isAdmin

static function isAdmin($userId = null): bool
{
	global $USER;

	if(!($USER instanceof CUser))
	{
		return false;
	}

	if(!$userId || $userId == $USER->getId())
	{
		if(Loader::includeModule('bitrix24'))
		{
			return $USER->CanDoOperation('bitrix24_config');
		}
		else
		{
			return $USER->IsAdmin();
		}
	}

	if(Loader::includeModule('bitrix24'))
	{
		// Bitrix24 context new style check
		return CBitrix24::IsPortalAdmin($userId);
	}
	else
	{
		//Check user group 1 ('Admins')
		$user = new CUser();
		$userGroups = $user::getUserGroup($userId);

		return in_array(1, $userGroups);
	}
}