php中变量的使用有关问题

php中变量的使用问题
从数据库中获得了各区的销售金额和销售数量，要对数量和金额求和。代码如下：

	ob_start();

	require_once 'DB.php';

	ob_end_clean();

	  $db=DB::Connect();

	$result=$db->QueryLastMonth();

   	$result1=$db->QueryLastMonthByArea();

	 $all_sales_amount;

	$all_sales_money;

	 echo  'begin '.$all_sales_amount;

	while($row1= sybase_fetch_assoc($result1))

	{

  ?>




				switch($row1["areacode"]){

				case "E":

				echo "华东区";

				break;

				case "C":

				echo "东北区";

				break;

				case "N":

				echo "华北区";

				break;

				case "W":

				echo "西大区(W)";

				break;

				case "H":

				echo "华中区";

				break;

				case "S":

				echo "华南区";

				break;

				case "F":

				echo "华东区(经销)";

				break;

				case "T":

				echo "西大区(T)";

				break;

				}

				?>





--

--





	 $all_sales_amount+=$row1["area_salesgoodssum"];

	 $all_sales_money+=$row1["area_salesmoney"];

	 echo '循环中数量'.$all_sales_amount."金额".$all_sales_money."
";

	 }

	 ?>