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 EventManager::getInstance()->addEventHandler('main', 'OnBeforeProlog', 'updateBasketLang');
 

 function updateBasketLang ()
{
   $request = Bitrix\Main\Application::getInstance()->getContext()->getRequest();
   if(strpos($request->getRequestUri(), "/bitrix") === false && !$request->isAjaxRequest())
   {
      if(\Bitrix\Main\Loader::includeModule('catalog') && \Bitrix\Main\Loader::includeModule('sale'))
      {
         $basket = \Bitrix\Sale\Basket::loadItemsForFUser(\Bitrix\Sale\Fuser::getId(), ['s1' , 's2' , 's3']);
         $basketItems = $basket->getBasketItems();
         foreach ($basketItems as $item)
         {
            $item->setField('LID', SITE_ID);
            $item->save();
         }
      }
   }
}