อยากรู้ค่ะว่าเราจะใช้ variable ที่มากับ link หน้านี้ ส่งค่าไปใช้อีกหน้านึงได้ยังไงอ่ะคะ

echo "<form action='index.php?argId=$argId' method=get id=sortBy name=sortBy>";
echo "sort by". "<select id=sortBy name=sortBy> <option value=choose>..choose..</option> <option value=prices>prices</option> <option value=name>name </option> </select>";
echo "<input type=submit value=GO!>";
echo "</form>";

$sort = htmlspecialchars($_GET[sortBy],ENT_QUOTES);
		$sortArg = "";
		if($sort != "")
		{
			if(strcmp($sort,"prices")==0)
			{
				$sortArg .= "ORDER BY Product_Prices ASC;";
			}
		
			else if(strcmp($sort,"name")==0)
			{
				$sortArg .= "ORDER BY Product_Name ASC";
			}
		}

		$argId=$_GET["argId"];
		$sql = "SELECT SQL_CALC_FOUND_ROWS * FROM product WHERE (Cat_Id ='$argId' OR Color_Id='$argId' OR Wearer_Id='$argId' OR Mat_Id='$argId' OR Product_Des LIKE '%".$argId."%') AND Size_Id='s1' LIMIT $start_row, $rows_per_page"."$sortArg";