require_once($_SERVER['DOCUMENT_ROOT'] . "/bitrix/modules/main/include/prolog_before.php");
 
CModule::IncludeModule("iblock");
CModule::IncludeModule("catalog");
 

$iblock_id = 16; 
$idPropSale = 213; 
 
$oldPropsSale = $arNewSale = array();
 

$resItem = CIBlockElement::GetList(
    array("ID"=>"asc"),
    array( "ACTIVE"=>"Y", "IBLOCK_ID"=>$iblock_id),
    false,
    false,
    array("ID", "IBLOCK_ID", "PROPERTY_SPECIALOFFER")
);
while($arItem = $resItem->Fetch())
{
    
    $oldPropsSale[$arItem["ID"]] = $arItem["PROPERTY_SPECIALOFFER_VALUE"];
     
    
    $offersExist = CCatalogSKU::getExistOffers($arItem["ID"], $arItem["IBLOCK_ID"]);
     
    
    if($offersExist[$arItem["ID"]] == 1)
    {
        
        $resSku = CCatalogSKU::getOffersList(
            $arItem["ID"],
            $arItem["IBLOCK_ID"],
            array("ACTIVE"=>"Y") 
        );
         
        
        if(!empty($resSku[$arItem["ID"]]))
        {
            
            foreach($resSku[$arItem["ID"]] as $sku)
            {
                
                $arDiscounts = CCatalogDiscount::GetDiscountByProduct($sku["ID"], array(2), "N", 1, SITE_ID);
                 
                
                if(!empty($arDiscounts))
                {
                    
                    $arNewSale[$sku["PARENT_ID"]] = "Y";
                    
                    break;
                }
            }
        }
    }
    else 
    {
        
        $arDiscounts = CCatalogDiscount::GetDiscountByProduct($arItem["ID"], array(2), "N", 1, SITE_ID);
        
        if(!empty($arDiscounts))
        {
            
            $arNewSale[$arItem["ID"]] = "Y";
        }
    }
}
 

foreach($arNewSale as $prodId => $propVal)
{
    
    if($oldPropsSale[$prodId] != "yes" && $propVal == "Y")
    {
        
        CIBlockElement::SetPropertyValuesEx($prodId, $iblock_id, array("SPECIALOFFER" => $idPropSale));
    }
}
 

foreach($oldPropsSale as $prodId => $propVal)
{
   
    if($oldPropsSale[$prodId] == "yes" && $arNewSale[$prodId] != "Y")
    {
        
        CIBlockElement::SetPropertyValuesEx($prodId, $iblock_id, array("SPECIALOFFER" => false));
    }
}