Remove Product Quantity's

[Dysan]

I'm trying to develop a simple shopping basket, how do I remove the quantity option from the following code, so that only one of each item can be purchased instead of 2 or more?

 

Also, if the product selected to add to basket, already exists in the shopping cart, how do I display a message notifying the user?

 

<?php

session_start();
$con = mysql_connect("localhost","ODBC","");
if (!$con)
{
  die(mysql_error());
}

function writeShoppingCart() {
$cart = $_SESSION['cart'];
if (!$cart) {
return '<p>You have no items in your shopping cart</p>';
} else {
// Parse the cart session variable
$items = explode(',',$cart);
$s = (count($items) > 1) ? 's':'';
return '<p>You have <a href="cart.php">'.count($items).' item'.$s.' in your shopping cart</a></p>';
}
}

$cart = $_SESSION['cart'];
if ($cart) {
$cart .= ','.$_GET['id'];
} else {
$cart = $_GET['id'];
}
$_SESSION['cart'] = $cart;


$cart = $_SESSION['cart'];
if ($cart) {
$items = explode(',',$cart);
$contents = array();
foreach ($items as $item) {
$contents[$item] = (isset($contents[$item])) ? $contents[$item] + 1 : 1;
}
}

$total = 0;
echo '<table>';

foreach ($contents as $id=>$qty) {
mysql_select_db("MP3", $con);
$result = mysql_query("SELECT * FROM books WHERE id = '$id'") or die("Your have an error because:<br />" . mysql_error());
$row = mysql_fetch_assoc($result);


echo '<tr>';
echo '<td><a href="cart.php?action=delete&id='.$id.'" class="r">Remove</a></td>';
echo '<td>'.$row['title'].' by '.$row['author'].'</td>';
echo '<td>£'.$price.'</td>';
echo '<td><input type="text" name="qty'.$id.'" value="'.$qty.'" size="3" maxlength="3" /></td>';
echo '<td>£'.($price * $qty).'</td>';
$total += $price * $qty;
echo '</tr>';
}
echo '</table>';
echo '<p>Grand total: £'.$total.'</p>';

?>