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."
";
	 }
	 ?>