Base::filterByParams

protected function filterByParams($ids, $filterIds = array(), $useSectionFilter = true)
{
	if (empty($ids))
	{
		return array();
	}

	$ids = array_values(array_unique($ids));
	// remove duplicates of already showed items
	if (!empty($filterIds))
	{
		$ids = array_diff($ids, $filterIds);
	}

	if (!empty($ids))
	{
		$filter = $this->filterFields;
		$filter['ID'] = $ids;

		$correctIds = array();
		$elementIterator = CIBlockElement::GetList(array(), $filter, false, false, array('ID'));
		while ($element = $elementIterator->Fetch())
		{
			$correctIds[] = $element['ID'];
		}

		if ($useSectionFilter && !empty($correctIds) && $this->arParams['SHOW_FROM_SECTION'] === 'Y')
		{
			$correctIds = $this->filterIdBySection(
				$correctIds,
				$this->arParams['IBLOCK_ID'],
				$this->arParams['SECTION_ID'],
				$this->arParams['PAGE_ELEMENT_COUNT'],
				$this->arParams['DEPTH']
			);
		}

		$correctIds = array_flip($correctIds);
		// remove invalid items
		foreach ($ids as $key => $id)
		{
			if (!isset($correctIds[$id]))
			{
				unset($ids[$key]);
			}
		}

		return array_values($ids);
	}
	else
	{
		return array();
	}
}