OrderAck::convert

public function convert($data)
{
	if(!is_array($data))
		throw new ArgumentTypeException("data", "array");

	$result = "";

	foreach($data as $item)
	{
		if(empty($item["ORDER_ID"]) || empty($item["ORDER_LINE_ITEM_ID"]))
			throw new SystemException("Wrong structure of ack data item");

		$result .=
			"tn".
			"tt".$item["ORDER_ID"]."n".
			"tt".$item["ORDER_LINE_ITEM_ID"]."n".
			"tn";
	}

	return $result;
}