SESSION PHP get proid - php

Question

I wanted to retrieve the proid thats in the session.
when i add to cart rdy to check out .
The proid seems cannot to be retrieve which show empty.
but it did count the item that i entered.
cause when i add 2 item in cart , it display 2 row.
please help me.
this is cart.php
if (isset($_SESSION['cart']))
{
$total = 0;
foreach($_SESSION['cart'] as $proid =>$x)
{
$results = mysqli_query($con,"Select * from product where Product_ID = $proid");
$myrow = mysqli_fetch_array($results);
$proid = $myrow['Product_ID'];
$productname = $myrow['Product_Name'];
$productprice= $myrow['Product_Price'];
$line_cost = $productprice * $x;
$total=$total+$line_cost;
?>
<li class = "cartlist">
<?php echo '<img src="data:image/jpeg;base64,' . base64_encode($myrow['Product_Pic']) . '" width="196" height="120">';?>
<p><span style = "font-weight: bold; font-size: 1.2em;">
<?php echo $productname ?>
</span></br />RM <?php echo $productprice;?>
</br />Quantity : <?php echo $x ?></br><a href='cart.php?proid=<?php echo $proid;?>&action=add'>Add </a> <a href ='cart.php?proid=<?php echo $proid;?>&action=remove'> Reduce </a></br>RM<?php echo $line_cost; ?> <br/>
</p> </li>
<?php
}
This is payment.php
i wanted to retrieve the proid and display the product name and total to the user.
print_r($_SESSION);
if (isset($_SESSION['cart']))
{
$total = 0;
foreach($_SESSION['cart'] as $proid =>$x)
{
$results = mysqli_query($con,"Select * from product where Product_ID = $proid");
$myrow = mysqli_fetch_array($results);
$productname = $myrow['Product_Name'];
$productprice= $myrow['Product_Price'];
$line_cost = $productprice * $x;
$total=$total+$line_cost;
?>
<tr>
<td><? echo $productname ?></td>
<td><? echo $x ?></td>
<td><? echo $line_cost ?></td>
</tr>
<?php
}
}
After adding a print_r($_SESSION['cart']); to the top of payment.php I get this output
Array ( [36] => 3 )