php购物车有关问题

  include ('book_sc_fns.php');

  // The shopping cart needs sessions, so start one

  session_start();



  @$new = $_GET['new'];



  if($new) {

    //new item selected

    if(!isset($_SESSION['cart'])) {

      $_SESSION['cart'] = array();

      $_SESSION['items'] = 0;

      $_SESSION['total_price'] ='0.00';

    }



    if(isset($_SESSION['cart'][$new])) {

      $_SESSION['cart'][$new]++;

    } else {

      $_SESSION['cart'][$new] = 1;

    }



    $_SESSION['total_price'] = calculate_price($_SESSION['cart']);

    $_SESSION['items'] = calculate_items($_SESSION['cart']);

  }



  if(isset($_POST['save'])) {

    foreach ($_SESSION['cart'] as $isbn => $qty) {

      if($_POST[$isbn] == '0') {

        unset($_SESSION['cart'][$isbn]);

      } else {

        $_SESSION['cart'][$isbn] = $_POST[$isbn];

      }

    }



    $_SESSION['total_price'] = calculate_price($_SESSION['cart']);

    $_SESSION['items'] = calculate_items($_SESSION['cart']);

  }



  do_html_header("Your shopping cart");



  if(($_SESSION['cart']) && (array_count_values($_SESSION['cart']))) {

    display_cart($_SESSION['cart']);

  } else {

    echo "
There are no items in your cart
";

  }



  $target = "index.php";



  // if we have just added an item to the cart, continue shopping in that category

  if($new)   {

    $details =  get_book_details($new);

    if($details['catid']) {

      $target = "show_cat.php?catid=".$details['catid'];

    }

  }

  display_button($target, "continue-shopping", "Continue Shopping");



  // use this if SSL is set up

  // $path = $_SERVER['PHP_SELF'];

  // $server = $_SERVER['SERVER_NAME'];

  // $path = str_replace('show_cart.php', '', $path);

  // display_button("https://".$server.$path."checkout.php",

  //                 "go-to-checkout", "Go To Checkout");



  // if no SSL use below code

  display_button("checkout.php", "go-to-checkout", "Go To Checkout");



  do_html_footer();

?>