processing shopping cart order

hi i have a shopping cart which i found on the net and did a few alters to it, the cart is working all fine so far, but what i wanted to know is how do i send the details of the the items in the cart to the checkout.php page if the user decides checkout, just to confirm what they have brought . Thanks

this is the code for my cart.

cart.php

<?php
@session_start();
if(isset($_SESSION['user_name']))

{
}
else
{
 echo "<B>You must login to continue with cart <a href='login.php'>Click Here To Login</a>";
exit;
}

      include("db.php");
            
      switch($_GET["action"])
      {
            case "add_item":
            {
                  AddItem($_GET["id"], $_GET["qty"]);
                  ShowCart();
                  break;
            }
            case "update_item":
            {
                  UpdateItem($_GET["id"], $_GET["qty"]);
                  ShowCart();
                  break;
            }
            case "remove_item":
            {
                  RemoveItem($_GET["id"]);
                  ShowCart();
                  break;
            }
            default:
            {
                  ShowCart();
            }
      }

      function AddItem($itemId, $qty)
      {
            // Will check whether or not this item
            // already exists in the cart table.
            // If it does, the UpdateItem function
            // will be called instead
            
            global $dbServer, $dbUser, $dbPass, $dbName;

            // Get a connection to the database
            $cxn = @ConnectToDb($dbServer, $dbUser, $dbPass, $dbName);
            
            // Check if this item already exists in the users cart table
            $result = mysql_query("select count(*) from cart where cookieId = '" . GetCartId() . "' and itemId = $itemId");
            $row = mysql_fetch_row($result);
            $numRows = $row[0];
            
            if($numRows == 0)
            {
                  // This item doesn't exist in the users cart,
                  // we will add it with an insert query

                  @mysql_query("insert into cart(cookieId, itemId, qty) values('" . GetCartId() . "', $itemId, $qty)");
            }
            else
            {
                  // This item already exists in the users cart,
                  // we will update it instead
                  
                  UpdateItem($itemId, $qty);
            }
      }
      
      function UpdateItem($itemId, $qty)
      {
            // Updates the quantity of an item in the users cart.
            // If the qutnaity is zero, then RemoveItem will be
            // called instead

            global $dbServer, $dbUser, $dbPass, $dbName;

            // Get a connection to the database
            $cxn = @ConnectToDb($dbServer, $dbUser, $dbPass, $dbName);
            
            if($qty == 0)
            {
                  // Remove the item from the users cart
                  RemoveItem($itemId);
            }
            else
            {
                  mysql_query("update cart set qty = $qty where cookieId = '" . GetCartId() . "' and itemId = $itemId");
            }
      }
      
      function RemoveItem($itemId)
      {
            // Uses an SQL delete statement to remove an item from
            // the users cart

            global $dbServer, $dbUser, $dbPass, $dbName;

            // Get a connection to the database
            $cxn = @ConnectToDb($dbServer, $dbUser, $dbPass, $dbName);
            
            mysql_query("delete from cart where cookieId = '" . GetCartId() . "' and itemId = $itemId");
      }
      
      function ShowCart()
      {
            // Gets each item from the cart table and display them in
            // a tabulated format, as well as a final total for the cart
            
            global $dbServer, $dbUser, $dbPass, $dbName;

            // Get a connection to the database
            $cxn = @ConnectToDb($dbServer, $dbUser, $dbPass, $dbName);
            
            $totalCost = 0;
            $result = mysql_query("select * from cart inner join items on cart.itemId = items.itemId where cart.cookieId = '" . GetCartId() . "' order by items.itemName asc");
            ?>
            <html>
            <head>
            <title> Your Shopping Cart </title>
            <script language="JavaScript">
            
                  function UpdateQty(item)
                  {
                        itemId = item.name;
                        newQty = item.options[item.selectedIndex].text;
                        
                        document.location.href = 'cart.php?action=update_item&id='+itemId+'&qty='+newQty;
                  }
            
            </script>
            </head>
            <body bgcolor="#ffffff">
            <h1>Your Shopping Cart</h1>
            
            
                  <?php
                  
                  while($row = mysql_fetch_array($result))
                  {
                        // Increment the total cost of all items
                        $totalCost += ($row["qty"] * $row["itemPrice"]);
                        ?>
                              
                                                <select name="<?php echo $row["itemId"]; ?>" onChange="UpdateQty(this)">
                                                <?php
                                                
                                                      for($i = 1; $i <= 20; $i++)
                                                      {
                                                            echo "<option> ";
                                                            if($row["qty"] == $i)
                                                            {
                                                                  echo " SELECTED ";
                                    }
                                                            echo ">" . $i . "</option>";
                                    }
                                    ?>
                              </select>
                                          
                                    
                                    
                              <?php echo $row["itemName"]; ?>
                                          
                                    
                  
<?php echo number_format($row["itemPrice"], 2, ".", ","); ?>
                                          
                                    
                                    
<font face="verdana" size="1" color="black">
<a href="cart.php?action=remove_item&id=<?php echo $row["itemId"]; ?>">Remove</a>
                                          
                                    
                              
<?php
      }
                  
      // Display the total
?>
                              
<a href= "javascript:history.back();" >&lt;&lt; Keep Shopping</a>
                                          

<b>Total: &pound; <?php echo number_format($totalCost, 2, ".", ","); ?></b>
                                          




<form name='form1' method='post' action='checkout.php'>
<?
$cartId=GetCartId();
?>

<input type='hidden' name='cartid' value="<?php echo "$cartId"; ?>">

<input type='submit' name='sub1' value='Check Out'>


</form>
</body>
</html>
<?php
}

?>