PHP更新购物车查询无效

I am creating a shopping cart for my ecommerce website, but in that my update query program is not working. If more than one product is present in my cart then it is not updating the price & product quantity. If one product is present then it is working fine. I am new in php. I am also attaching the screenshot of my cart.

// cart.php

<?php include_once("header.php");?>
<div id="products_box">
 <form action="" method="post" enctype="multipart/form-data">

 <table align="center" width="700" bgcolor="#CCFFCC">
 <br>
 <tr align="center">
  <td style="font-family:'Adobe Garamond Pro', 'Times New Roman'; font-size:20px" colspan="4"><h2> Your Book(s) Details </h2></td>
 </tr>

 <tr align="center" style="font-size:20px; font-family:'Adobe Garamond Pro', 'Times New Roman'">
 <th>Remove</th>
 <th>Book(s)</th>
 <th>Quantity</th>
 <th>Total Price</th>
 </tr>

 <?php
 $total=0;
 global $con;
 $ip = getIp();
 $sel_price = "select * from cart where ip_add='$ip'";
 $run_price = mysqli_query($con, $sel_price) or die(mysqli_error($con));

  while($p_price = mysqli_fetch_array($run_price))
 {
  $b_id = $p_price['cb_id'];
  $b_price = "select * from books where b_id='$b_id'";
  $run_book_price = mysqli_query($con, $b_price) or die(mysqli_error($con));

  while($pp_price = mysqli_fetch_array($run_book_price))
  {
   $b_price = array($pp_price['b_price']);
   $b_title = $pp_price['b_title'];
   $b_image = $pp_price['b_image'];
   $single_price = $pp_price['b_price'];

   $values = array_sum($b_price);
   $total += $values;

 ?>

 <tr align="center"> 
 <td><input type="checkbox" name="remove[]"  value="<?php echo $b_id; ?>"/> </td>
 <td><h3><a href='details.php?b_id=$b_id' style='text-decoration:none; color: #005680;'><?php echo $b_title; ?></a></h3>
 <img src="admin_area/books_images/<?php echo $b_image; ?>" width="100" height="100" />
 </td>
 <td><input type="text" name="qty"  size="8" value=""/></td>
 <?php
  if(isset($_POST['update_qty']))
 { 

   $qty = $_POST['qty'];
   $update_qty = "update cart set qty='$qty'";
   $run_qty = mysqli_query($con, $update_qty) or die(mysqli_error($con));
   $total = $total*$qty;

 }

 ?>
 <td> <?php echo "Rs.
". $single_price; ?></td>
 </tr>

 <?php  } }?>

 <tr align="right">
   <td colspan="4"><b> Sub Total: </b></td>
   <td colspan="4"><?php echo "Rs.
". $total; ?></td>
  </tr>


  <tr>
  <td align="left" style="padding-left:12px"><input type="submit" name="remove_pro" value="Remove" style="background: #000000; font-family:'Adobe Garamond Pro Bold', 'Adobe Garamond Pro', 'Adobe Caslon Pro'; font-size:18px; color:#FFFFFF"/></td>


  <td align="center" style="padding-right:20px"><input type="submit" name="continue" value="Continue Shopping" style="background: #000000; font-family:'Adobe Garamond Pro Bold', 'Adobe Garamond Pro', 'Adobe Caslon Pro'; font-size:18px; color:#FFFFFF" /></td>


   <td align="center" style="padding-left:12px"><input type="submit" name="update_qty" value="Update Quantity" style="background: #000000; font-family:'Adobe Garamond Pro Bold', 'Adobe Garamond Pro', 'Adobe Caslon Pro'; font-size:18px; color:#FFFFFF"/></td>


  <td align="right" colspan="4"><input type="submit" name="checkout" value="Checkout" style="background: #000000; font-family:'Adobe Garamond Pro Bold', 'Adobe Garamond Pro', 'Adobe Caslon Pro'; font-size:18px; color:#FFFFFF; margin-right:10px"/></td>
  </tr>

 </table>

 </form>


 <?php

  global $con;
  $ip = getIp();

  if(isset($_POST['remove_pro']))
 {
  foreach($_POST['remove'] as $remove_id)
 {
  $delete_pro = "delete from cart where cb_id='$remove_id' AND ip_add='$ip'";
  $run_query = mysqli_query($con, $delete_pro) or die(mysqli_error($con));
  if($run_query)
  {
   echo "<script>window.open('cart.php','_self')</script>";
  }
 }
}

 if(isset($_POST['continue']))
{
 echo "<script>window.open('index.php','_self')</script>";
}

 if(isset($_POST['checkout']))
{
 echo "<script>window.open('checkout.php','_self')</script>";
}


 ?>

</div>


</div>



</div>
<!--Content Wrapper Ends--->


<?php include_once("footer.php");?>
<!--Main Wrapper Ends-->


</body>

</html>