ช่วยหน่อยครับ add to cart ไม่ได้ ทำมาหลายวันละ คือผมทำ Add to cart ครับ กรอกจำนวนสินค้าใน Text Field

<?php
     //======Step 1  ChkOrder =========
		 $sql="select * from cart  where CustId='".$CustId."' ";
		 $result=mysql_query($sql);
		 $num_row=mysql_num_rows($result);
		 $row=mysql_fetch_array($result);
		 $ChkOrder=$row['OrderId'];
		 if($num_row==0){
				   //$sql="update ChkOrder set  ChkOrder=ChkOrder + 1 ";
			 	  //mysql_query($sql);
				  //$sql="select  max(ChkOrder)  from  ChkOrder ";
				   
				   $sql="select  max(OrderId) as MaxQ  from  orders where OrderId like 'B".date('ymd')."%' ";
				   $result1=mysql_query($sql);
 				   $row1=mysql_fetch_array($result1);
				   $ChkOrder=$row1['MaxQ'];
				   if($ChkOrder==""){
				   	   $ChkOrder="B".date('ymd')."001";
				   }else{
				   	   $T=substr($ChkOrder,8,3);
					   $T=$T+1;
					   $T=sprintf("%03d",$T);
					   $ChkOrder="B".date('ymd').$T;
				   }
          }  // ä´é  orderid  ãËÁ

            	if(trim($ProductID1)!=""){
							$sql="select  * from  cart    where  ProductID='".trim($ProductID1)."'  and   CustId='".trim($CustId)."'  ";
							$result=mysql_query($sql) or die(mysql_error());
							$nro=mysql_num_rows($result);
							if($nro==0){
									$sql="insert  into  cart  (OrderId,CustId,ProductID,Amount,BuyPrice,TimeOut)
									values('".$ChkOrder."','".$CustId."','".trim($ProductID1)."','".trim($Amount)."','".$BuyPrice."','".time()."')"; 
									mysql_query($sql)  or die(mysql_error());
			 		       }//if($nro==0){
				}//if(trim($ProductId) !=""){

       header("Location:cart.php");

?>