A litle help with shopping cart

hi,

i have a shopping cart with this SQL queries:

<?php
session_start();
$sessionid = session_id();
$code = $_POST["code"];
$model = $_POST["model"];
$descr = $_POST["descr"];
$pricer = $_POST["pricer"];
$qty = $_POST["qty"];
$cart = $_POST["cart"];
If($qty == "") $qty=1; ?>

<?php
if ( !empty($cart) ) {
  switch($cart) {
    case "add":
      $sql= "INSERT INTO cart (sessionid, code, model, descr, pricer, qty) VALUES ('$sessionid','$code','$model','$descr','$pricer','$qty')";
      break;
    case "del":
      $sql= "DELETE FROM cart WHERE code='$code'";
      break;
    case "upd":
      $sql= "UPDATE cart SET qty='$qty' WHERE code='$code'";
      break;
  }
  if ( !empty($sql) ) {
    $res= mysql_query($sql);
    // handle any query errors here
  }
}

$result = mysql_query("SELECT * FROM cart WHERE sessionid='".$sessionid."' ORDER BY pricer");

mysql_close($con);
?>

PHP:

i want to display a message when the visitor adds a product for second time in the cart. when the product is already in the cart i want to display a message like that: "the product is already in the cart"

can anybody give a litle help?

thanks in advance.

 

<?phpsession_start();$sessionid = session_id();$code = $_POST["code"];$model = $_POST["model"];$descr = $_POST["descr"];$pricer = $_POST["pricer"];$qty = $_POST["qty"];$cart = $_POST["cart"];If($qty == "") $qty=1; ?>
if ($cart=="add")
{

$result2=mysql_query("SELECT * FROM cart WHERE sessionid='".$sessionid."' ORDER BY pricer");
$tt=0;
while ($row = mysql_fetch_array($result2)) { 
if ($row["code"]==$code)
{
$tt=1;

}

} //while
if ($tt==1)
echo "product allready added";

}

<?php
if ( !empty($cart) )
 {
  switch($cart)
 {
    case "add":
      $sql= "INSERT INTO cart (sessionid, code, model, descr, pricer, qty) VALUES ('$sessionid','$code','$model','$descr','$pricer','$qty')"; 
     break; 
   case "del":
      $sql= "DELETE FROM cart WHERE code='$code'";   
   break;
    case "upd": 
     $sql= "UPDATE cart SET qty='$qty' WHERE code='$code'"; 
     break; 
 } 
 if ( !empty($sql) ) 
{ 
if($tt==0)
   $res= mysql_query($sql);   
 // handle any query errors here 
 }
}
$result = mysql_query("SELECT * FROM cart WHERE sessionid='".$sessionid."' ORDER BY pricer");
mysql_close($con);
?>

Code (markup):

 

you are the man. thank you very match.