PHP - รบกวนหน่อยคับ เรื่องการคิดราคารวมอะคับ

<table class="table table-bordered">
                	<tr>
                    	<td colspan="5"><? echo $process_category_name;?></td>
                    </tr>
                    <tr>
                        <td width="5%"> ลำดับ</td><td width="55%">รายการสินค้า</td><td width="10%">ราคา</td><td width="15%">จำนวน</td><td width="15%">ยอดรวม</td>
                    </tr>

                    <?php  
				
							$qr_x =dbQuery("SELECT * FROM tbl_product where process_category_id = '$process_category_id' ORDER BY product_name ASC");	
							$row =@mysql_num_rows($qr_x);
							 $i=0;
							while ($i<$row){
							$rs_x=mysql_fetch_array($qr_x);
							$product_id = $rs_x['product_id'];
							$product_name = $rs_x['product_name'];
							$price = $rs_x['price'];
							
				?>                       
                     <tr>
                        <td width="5%"><? echo $i+1;?></td><td width="55%"><? echo $product_name;?></td><td width="10%"><? echo $price;?>
                        <input type="hidden" name="price<?=$product_id;?>"  value="<? echo $price;?>" size="2" onfocus="startCalc<?=$product_id;?>()" onblur="stopCalc<?=$product_id;?>()"></td><td width="15%">
                        <input type="number" class="form-control" min="0" name="num<?=$product_id;?>" size="2" onfocus="startCalc<?=$product_id;?>()" onblur="stopCalc<?=$product_id;?>()" ></td><td width="15%">
                        <input type="text" name="sum_price<?=$product_id;?>"  class="input-label" size="2" value="0"  disabled="disabled"></td>
                    </tr>
<SCRIPT Language="JavaScript">
function startCalc<?=$product_id;?>(){ 
interval = setInterval("calc<?=$product_id;?>()",1); 
} 
function calc<?=$product_id;?>(){ 
num<?=$product_id;?> = document.autoSumForm.num<?=$product_id;?>.value; 
price<?=$product_id;?> = document.autoSumForm.price<?=$product_id;?>.value; 
document.autoSumForm.sum_price<?=$product_id;?>.value = (num<?=$product_id;?>) * (price<?=$product_id;?>); 

} 
function stopCalc<?=$product_id;?>(){ 
clearInterval(interval); 
} 
</SCRIPT>



                    <?
					$i++;
							}
					?>
                </table>