$cart = $_SESSION['cart'];
$action = $_GET['action'];
switch ($action) {
	case 'add':
		if ($cart) {
			$cart .= ','.$_GET['id'];
		} else {
			$cart = $_GET['id'];
		}
		break;
	case 'delete':
		if ($cart) {
			$items = explode(',',$cart);
			$newcart = '';
			foreach ($items as $item) {
				if ($_GET['id'] != $item) {
					if ($newcart != '') {
						$newcart .= ','.$item;
					} else {
						$newcart = $item;
					}
				}
			}
			$cart = $newcart;
		}
		break;
}
$_SESSION['cart'] = $cart;