Why does the event in Bitrix not work?

Question

1C-Bitrix

Good afternoon
The task is to change the price when unloading, in init.php added such an event

AddEventHandler("catalog", "OnBeforePriceUpdate", array("MyClass", "OnBeforePriceUpdateHandler"));
class MyClass {
   function OnBeforePriceUpdateHandler($PRICE_ID, $arFields)
      {
         $NewPrice = 5000;
         $arPrice = array(
            "PRODUCT_ID" => $arFields['PRODUCT_ID'],
            "CATALOG_GROUP_ID" => 1,
            "PRICE" => $NewPrice,
            "CURRENCY" => "RUB"
         );
         CPrice::Update($PRICE_ID, $arPrice);
      }
}

but for some reason it causes a 500 error
. I also tried this event:

AddEventHandler("catalog", "OnBeforePriceUpdate", array("MyClass", "OnBeforePriceUpdateHandler"));
class MyClass
{
   function OnBeforePriceUpdateHandler($PRICE_ID, $arFields)
   {
      $db_price = CPrice::GetList(
         array(),
         array(
            "ID" => $PRICE_ID
         )
      );
      if($ar_price = $db_price->Fetch())
      {
         if($ar_price['PRICE'] != $arFields['PRICE'])
         {
            $arFields['PRICE']=$arFields['PRICE']/100*110;
         }
      }
   }
}

but it didn't work at all

Answer 1

In the first case, you get a loop of handler calls.

Answer 2

Just change the value of the field and return that value.
OnBeforePriceUpdateHandler($PRICE_ID, & $arFields) - write in such a way that you get an array by reference and change its value, and not work in another instance.
Fix it and use the second option