Client::getProductSkuIds

protected function getProductSkuIds($productIds)
{
	if (!Loader::includeModule("catalog"))
		return [];

	return
		array_reduce(
			\CCatalogSKU::getOffersList($productIds),
			function($ids, $items)
			{
				$ids = array_merge(
					$ids,
					array_map(
						function($item)
						{
							return $item['ID'];
						},
					$items)
				);
				return $ids;
			}, []);
}