Kyle Bean's paypal plugin

cart.php

<?php
function get_cart() {
    s::start();
    $cart = s::get('cart', array());
    return $cart;
}

function cart_logic($cart) {

    if (isset($_REQUEST['action'])) {
      $action = $_REQUEST['action'];
      $id = $_REQUEST['id'];
      switch ($action) {
          case 'add':
              if (isset($_REQUEST['quantity'])) {
                $quantity = intval($_REQUEST['quantity']);
                if (isset($cart[$id])) {
                    $cart[$id] + intval($quantity);
                } else {
                    $cart[$id] = intval($quantity);
                }
              }
              break;
          case 'remove':
              if (isset($cart[$id])) {
                  $cart[$id]--;
              } else {
                  $cart[$id] = 1;
              }
              break;
          case 'update':
              if (isset($_REQUEST['quantity'])) {
                  $quantity = intval($_REQUEST['quantity']);
                  if ($quantity < 1) {
                      unset($cart[$id]);
                  } else {
                      $cart[$id] = $quantity;                
                  }
              }
              break;
          case 'delete':
              if (isset($cart[$id])) {
                  unset($cart[$id]);
              }
              break;
      }
      s::set('cart', $cart);
    }

    if (count($cart) == 0) {
        go(url('shop'));        
    }

    return $cart;
}

function cart_count($cart) {
    $count = 0;
    foreach ($cart as $id => $quantity) {
        $count += $quantity;
    }
    return $count;
}

function cart_postage($total) {
    $postage;
    switch ($total) {
        case ($total < 10):
            $postage = 2.5;
            break;
        case ($total < 30):
            $postage = 3.5;
            break;
        case ($total < 75):
            $postage = 5.5;
            break;
        case ($total < 150):
            $postage = 8;
            break;
        default:
            $postage = 10;
    }
    return $postage;
}
?>