Cookie::getCookieDomain

static function getCookieDomain()
{
	static $domain = null;

	if ($domain !== null)
	{
		return $domain;
	}

	$request = BitrixMainContext::getCurrent()->getRequest();

	$httpHost = $request->getHttpHost();

	$cacheFlags = ConfigConfiguration::getValue('cache_flags');
	$cacheTtl = ($cacheFlags['site_domain'] ?? 0);

	if ($cacheTtl === false)
	{
		$connection = BitrixMainApplication::getConnection();
		$sqlHelper = $connection->getSqlHelper();

		$sql = "SELECT DOMAIN ".
			"FROM b_lang_domain ".
			"WHERE '".$sqlHelper->forSql('.'.$httpHost)."' like ".$sqlHelper->getConcatFunction("'%.'", "DOMAIN")." ".
			"ORDER BY ".$sqlHelper->getLengthFunction("DOMAIN")." ";
		$recordset = $connection->query($sql);
		if ($record = $recordset->fetch())
		{
			$domain = $record['DOMAIN'];
		}
	}
	else
	{
		$managedCache = BitrixMainApplication::getInstance()->getManagedCache();

		if ($managedCache->read($cacheTtl, 'b_lang_domain', 'b_lang_domain'))
		{
			$arLangDomain = $managedCache->get('b_lang_domain');
		}
		else
		{
			$arLangDomain = ['DOMAIN' => [], 'LID' => []];

			$connection = BitrixMainApplication::getConnection();
			$sqlHelper = $connection->getSqlHelper();

			$recordset = $connection->query(
				"SELECT * ".
				"FROM b_lang_domain ".
				"ORDER BY ".$sqlHelper->getLengthFunction("DOMAIN")
			);
			while ($record = $recordset->fetch())
			{
				//it's a bit tricky, the cache is used somewhere else, that's why we have the LID key here.
				$arLangDomain['DOMAIN'][] = $record;
				$arLangDomain['LID'][$record['LID']][] = $record;
			}
			$managedCache->set('b_lang_domain', $arLangDomain);
		}

		foreach ($arLangDomain['DOMAIN'] as $record)
		{
			if (strcasecmp(mb_substr('.'.$httpHost, -(mb_strlen($record['DOMAIN']) + 1)), ".".$record['DOMAIN']) == 0)
			{
				$domain = $record['DOMAIN'];
				break;
			}
		}
	}

	if ($domain === null)
	{
		$domain = '';
	}

	return $domain;
}