Network::isUserAdmin

static function isUserAdmin($userId)
{
	static $isAdmin = [];
	if (!isset($isAdmin[$userId]))
	{
		$user = self::getCurrentUser();
		if (MainLoader::includeModule('bitrix24'))
		{
			if (
				$user->isAuthorized()
				&& $user->getId() === $userId
				&& $user->isAdmin()
			)
			{
				$result = true;
			}
			else
			{
				$result = CBitrix24::isPortalAdmin($userId);
			}
		}
		else
		{
			if ($user->isAuthorized() && $user->getId() === $userId)
			{
				$result = $user->isAdmin();
			}
			else
			{
				$result = false;

				$groups = MainUserTable::getUserGroupIds($userId);
				foreach ($groups as $groupId)
				{
					if ($groupId == 1)
					{
						$result = true;
						break;
					}
				}
			}
		}

		$isAdmin[$userId] = $result;
	}

	return $isAdmin[$userId];
}