Problem with PHP shopping cart and MySQL Database

[Heather]

🙁
Please help!! I'm trying to implement a shopping cart. My problem is that I have to store the total order amount from the php shopping cart in a table in MySQL. I have a table set up to hold the session information which stores the product code and the quantity ordered along with the session id. I'm not sure whether to store the total order amount here or whether to put it in a different table. In either case I don't know how to put the order total in. Here is the code that I'm using:

my_shoppingcart.php
<?
// To include this shopping cart, use include("my_shoppingcart.php");

// Please note the parameters that you will need to call each function with.
// Every function here needs a $table and $session parameter to be passed in.

// You should create a $table variable in the script that calls this class to

// designate the table you are working with.

// Establishes the session variable so we know who is roaming around the web site.
// this session will only be established the first time that the parent page is loaded.

if(!$session && !$ShoppingCart) //make sure this hasn't already been established
{
$session = md5(uniqid(rand())); //creates a random session value

// sets a cookie with the value of session.

// set the cookie to remain for 30 minutes
SetCookie( "ShoppingCart", "$session",time()+1800);
}
class Cart
{

function add_item($table,$session,$product,$quantity)
{
// Checks to see if they already have that product in their list
$in_list = "SELECT * FROM $table WHERE session='$session' ";
$in_list .= "AND product='$product'";
$result = mysql_query( "$in_list");
$num_rows = mysql_num_rows($result);

        // they don't have that product in their cart?  Put it in. 
       if($num_rows == 0)
       {
          $sql =  "INSERT INTO $table (session,product,quantity) VALUES ";
          $sql .=  "('$session','$product','$quantity')";
          mysql_query( "$sql");
       }
        // They have the product in their cart already?  Add the quantity they specified 
        // to the product they have in their cart 
       else
       {
          $row = mysql_fetch_array($result);
          $quantity = $quantity + $row[quantity];
          $sql =  "UPDATE $table SET quantity='$quantity' WHERE ";
          $sql .=  "session='$session' AND product='$product'";
          mysql_query( "$sql");
       }
    }
     // delete a specified item 
    function delete_item($table,$session,$product)
    {
       mysql_query( "DELETE FROM $table WHERE session='$session' AND product='$product'");
    }
     // modifies a quantity of an item 
    function modify_quantity($table, $session, $product, $quantity)
    {
       $sql =  "UPDATE $table SET quantity='$quantity' ";
       $sql .=  "WHERE session='$session' AND product='$product'";
       mysql_query( "$sql");
    }
     // clear all content in their cart 
    function clear_cart($table,$session)
    {
       mysql_query( "DELETE FROM $table WHERE session='$session'");
    }
     //add up the shopping cart total 
    function cart_total($table,$session)
    {
       $result = mysql_query( "SELECT * FROM $table WHERE session='$session'");
       if(mysql_num_rows($result) >0)
       {
          while($row = mysql_fetch_array($result))
          {
              // look up the item in inventory 
             $price_from_inventory =  "SELECT price FROM inventory WHERE ";
             $price_from_inventory .=  "product = '$row[product]'";
             $result_inventory = mysql_query( "$price_from_inventory");
             $row_price = mysql_fetch_array($result_inventory);
              //calculate the total 
             $total = $total + ($row_price[price]*$row[quantity]);
          }
       }
       return $total;
       }
     function display_contents($table,$session)
     {
     $count = 0;
     $result = mysql_query( "SELECT * FROM $table WHERE session='$session'");
     while($row = mysql_fetch_array($result))
     {
        $result_inv = mysql_query( "SELECT * FROM inventory WHERE product='$row[product]'");
        $row_inventory = mysql_fetch_array($result_inv);
        $contents[ "product"][$count] = $row_inventory[product];
        $contents[ "price"][$count] = $row_inventory[price];
        $contents[ "quantity"][$count] = $row[quantity];
        $contents[ "total"][$count] = ($row_inventory[price] * $row[quantity]);
        $count ++;
     }
      $total = $this->cart_total($table,$session);
      $contents[ "final"] = $total;
      return $contents;
     }
     function num_items($table, $session)
     {
        $result = mysql_query( "SELECT * FROM $table WHERE session='$session'");
        $num_rows = mysql_num_rows($result);
        return $num_rows;
     }
}

?>

my_view_cart.php
<?
mysql_connect("localhost", "username", "password");
mysql_select_db( "my_db");
include( "my_shoppingcart.php");
$table = "sales_order";
$cart = new Cart;

if($add)
{
if($ShoppingCart)
$session = $ShoppingCart;

 $result = mysql_query(  "SELECT * FROM inventory WHERE product='$add'");
 $row = mysql_fetch_array($result);

 $cart->add_item($table,$session,$row[product],1);

}

if($remove)
{
if($ShoppingCart)
{
$session = $ShoppingCart;
}

 $result = mysql_query(  "SELECT * FROM inventory WHERE product='$remove'");
 $row = mysql_fetch_array($result);
 $cart->delete_item($table,$session,$row[product]);

}
if($modify)
{
$contents = $cart->display_contents($table,$session);
for($i = 0; $i < sizeof($quantity); $i++)
{
$oldquan = $contents[quantity][$i];
$product = $contents[product][$i];
$newquan = $quantity[$product];
$cart->modify_quantity($table,$session,$product,$newquan);
}
}
// End update cart

?>
<html>
<head>
<title>Shopping Cart</title>
<link rel="stylesheet" href="text_box.css" type="text/css">
<link rel="stylesheet" href="lotto.css" type="text/css">
</head>

<style>
<!--
.MyScrolls
{
scrollbar-base-color:#990000;
scrollbar-face-color:#990000;
scrollbar-shadow-color:#FFCC99;
scrollbar-highlight-color:#FFCC99;
scrollbar-3dlight-color:#990000;
scrollbar-darkshadow-color:#990000;
scrollbar-track-color:#FFCC99;
scrollbar-arrow-color:#FFCC99;
}
-->
</style>
<body bgcolor="#990000" link="#FFCC99" alink="#FFCC99" vlink="#FFCC99" text="#FFCC99" class="MyScrolls">
<?
$url = $PHP_SELF;
if(!$ShoppingCard)
$url .= "?session=$session";
echo "<FORM ACTION=$url method=post>\n";
?>
<a name="top"></a>

<table align=center border="0" cellpadding="5" cellspacing="0">

<font size="6" face="Copperplate Gothic Bold"><CENTER>Shopping
Cart Items</font></td>
</center>
</TABLE>
<p><center><TABLE BORDER=1 cellpadding=2></center>
<TR>

<TD><font size="4" face="Copperplate Gothic Bold">Product</font></TD>
<TD><font size="4" face="Copperplate Gothic Bold">Price</font></TD>
<TD><font size="4" face="Copperplate Gothic Bold">Quantity</font></TD>
<TD><font size="4" face="Copperplate Gothic Bold">Total</font></TD>
<TD>&nbsp;</TD>

<?

if($ShoppingCart)
{

$session = $ShoppingCart;
}

$contents = $cart->display_contents($table,$session);
if($contents[product][0] != "")
{
$x = 0;
while($x != $cart->num_items($table,$session))
{
echo "<TR><TD>".$contents[product][$x]. "</TD><TD>&euro;".$contents[price][$x]. "</TD>\n";
$product = $contents[product][$x];
echo "<TD><INPUT TYPE=text size=3 name=quantity[$product] ";
echo "value=\"".$contents[quantity][$x]. "\"></TD>";
echo "<TD>&euro;".$contents[total][$x]. "</TD>\n";
echo "<TD><A HREF=\"my_view_cart.php?remove=".urlencode($contents[product][$x]);
echo "".(!$ShoppingCart? "&session=$session": ""). "\">Remove</A>";
$x ++;

}
echo  "</TD><TR></TABLE>";
echo  "<BR><B><center>Total Order Amount: &euro;".$cart->cart_total($table,$session). "</center></B>";
echo  "<BR><center><INPUT TYPE=submit name=modify value=\"Recalculate Order\"></center>";
echo  "<BR><BR>";

}

else

echo "<p><center>There are no items in your shopping cart.</center>";
?>

</FORM>
</BODY>
</HTML>

I'm not sure how to insert the total order amount into the database. I would be grateful if anyone out there could help me, I'm quite new to this!!