Network::getNetworkId

static function getNetworkId($userId)
{
	$result = BitrixMainUserTable::getById($userId);
	$user = $result->fetch();
	if (!$user || $user['EXTERNAL_AUTH_ID'] != self::EXTERNAL_AUTH_ID)
	{
		return null;
	}

	list($networkId, ) = explode('|', $user['XML_ID']);

	return $networkId;
}