Подписывание на события системы - sidigi/bitrix-info GitHub Wiki

<?php
$eventManager = Bitrix\Main\EventManager::getInstance();
/*module - iblock, event name - OnBeforeIBlockElementAdd and callback */
$eventManager->addEventHandler('iblock', 'OnBeforeIBlockElementAdd', function(&$arFields){
  //here your code
});
//for ORM
$eventManager->addEventHandler("main", "\SomePartner\MyBooksCatalog\Book::OnBeforeUpdate", function(){
  //here your code 
});