undefined variable sub_total. even after defining the variable - php

Question

<?php
include('includes/db.php');
?>
<?php include('functions/functions.php'); ?>
<?php
include('header.php');
?>
<?php
include('topheader.php');
?>
<?php
include('nav.php');
?>
<div id="content">
<div class="container">
<div class="col-md-12">
<ul class="breadcrumb">
<li>Home</li>
<li>Cart</li>
</ul> <!--breadcrumb ends--->
</div> <!---col-md-12 ends-->
<div class="col-md-9" id="cart">
<div class="box">
<form action="cart.php" method="post" enctype="multipart-form-data">
<h1>Shopping Cart</h1>
<?php
$ip_add = getUserIP();
$select_cart = "select * from cart where ip_add='$ip_add'";
$run_cart = mysqli_query($conn, $select_cart);
$count = mysqli_num_rows($run_cart);
?>
<p class="text-muted">You currently have <?php echo $count; ?> items in your cart</p>
<div class="table-responsive">
<table class="table">
<thead>
<tr>
<th colspan="2">Product</th>
<th>Quantity</th>
<th colspan="1">Unit Price</th>
<th>Container</th>
<th colspan="1">Delete</th>
<th colspan="2">Sub Total</th>
</tr>
</thead> <!--thead ends-->
<tbody>
<?php
$total = 0;
while ($row_cart = mysqli_fetch_array($run_cart)) {
$pro_id = $row_cart['p_id'];
$pro_size = $row_cart['size'];
$pro_qty = $row_cart['qty'];
$get_products = "select * from products where product_id='$pro_id'";
$run_products = mysqli_query($conn, $get_products);
while ($row_products = mysqli_fetch_array($run_products)) {
$product_title = $row_products['product_title'];
$product_img1 = $row_products['product_img1'];
$only_price = $row_products['product_price'];
$sub_total = $row_products['product_price'] * $pro_qty;
$total += $sub_total;
}
?>
<tr>
<td><img src="admin_area/product_images/<?php echo $product_img1; ?>"></td>
<td><?php echo $product_title; ?></td>
<td><?php echo $pro_qty; ?></td>
<td>₹<?php echo $only_price; ?>.00</td>
<td><?php echo $pro_size ?></td>
<td><input type="checkbox" name="remove[]" value="<?php echo $pro_id; ?>"></td>
<td>₹<?php echo $sub_total; ?>.00</td>
</tr> <!---tr ends-->
<?php } ?>
</tbody>
<tfoot>
<tr>
<th colspan="5">TOTAL</th>
<th colspan="2">₹ <?php echo $total; ?>.00</th>
</tr>
</tfoot> <!--tfoot ends-->
</table> <!--table ends-->
</div> <!---table-responsive end-->
<div class="box-footer">
<div class="pull-left">
<a href="index.php" class="btn btn-default">
<i class="fa fa-chevron-left"></i>Continue Shopping
</a>
</div> <!--pullleft ends-->
<div class="pull-right">
<button class="btn btn-default" type="submit" name="update" value="Update Cart"><i class="fa fa-refresh"></i>Update Cart </button>
<a href="checkout.php" class="btn btn-primary">
Proceed to checkout<i class="fa fa-chevron-right"></i>
</a>
</div> <!--pullright ends-->
</div> <!----box footer ends-->
</form> <!---form ends-->
</div> <!---box ends-->
<?php
function update_cart() {
global $conn;
if (isset($_POST['update'])) {
foreach ($_POST['remove'] as $remove_id) {
$delete_product = "delete from cart where p_id='$remove_id'";
$run_delete = mysqli_query($conn, $delete_product);
if ($run_delete) {
echo "<script>window.open('cart.php','_self')</script>";
}
}
}
}
echo #$up_cart = update_cart();
?>
<div class="row same-height-row">
<div class="col-md-3 col-md-6">
<div class="box same-height headline">
<h3 class="text-center">Recently Viewed Product</h3>
</div> <!----box same-height headline end-->
</div> <!---col-m-3 col-md-6 ends---->
<?php
$get_products = "select * from products order by rand() LIMIT 0,3";
$run_products = mysqli_query($conn, $get_products);
while ($row_products = mysqli_fetch_assoc($run_products)) {
$pro_id = $row_products['product_id'];
$pro_title = $row_products['product_title'];
$pro_price = $row_products['product_price'];
$pro_img1 = $row_products['product_img1'];
echo "<div class='center-responsive col-md-3 col-sm-6'>
<div class='product same-height'>
<a href='details.php?pro_id=$pro_id'>
<img src='admin_area/product_images/$pro_img1' class='img-responsive'>
</a>
<div class='text'>
<h3><a href='details.php?pro_id=$pro_id'>$pro_title</a></h3>
<p class='price'>₹ $pro_price</p>
</div>
</div>
</div>";
}
?>
</div>
</div>
<div class="col-md-3">
<div class="box" id="order-summary">
<div class="box-header">
<h3>Order Summary</h3>
</div> <!--box-header ends-->
<p class="text-muted">
Shipping and additional costs are calulated based on the value you have entered.
</p>
<div class="table-responsive">
<table class="table">
<tbody>
<tr>
<td>Order Subtotal</td>
<th>₹<?php echo $sub_total; ?></th>
</tr>
<tr>
<td>Shipping and Handling</td>
<td>₹0.00</td>
</tr>
<tr>
<td>Tax</td>
<td>₹0.00</td>
</tr>
<tr class="total">
<td>Total</td>
<th>₹ <?php echo $total; ?></th>
</tr>
</tbody>
</table> <!--table ends-->
</div> <!---table responsive ends-->
</div> <!---box ends-->
</div> <!----col-md-3 ends--->
</div> <!--container ends-->
</div> <!---content ends-->
<?php include_once 'footer.php'; ?>
i get undefined variable sub_total even after defining variable subtotal above. Can someone figure out what the problem is?? I have check all curly brackets and semicolen. Due on a project that needs to be submited tomorrow. I am thinking improving the coding later but the basic functionality is not working.