ShoppingCart.php

<?php

//as soon as shopping cart is referenced the session context is created
SessionContext::create();

/**
 * ShoppingCart
 * 
 * 
 * @package    
 * @subpackage 
 * @author     John Doe <jd@fbi.gov>
 */
class ShoppingCart extends BaseObject {

  /**
   * add an item to the shopping cart
   * 
   * @param integer $bookId book id
   * @return null
   */
  public static function add($bookId) {
    $c = self::getCart();
    $c[$bookId] = $bookId;
    self::storeCart($c);
  }

  /**
   * remove an item from the shopping cart
   * 
   * @param integer $bookId book id
   * @return null
   */
  public static function remove($bookId) {
    $c = self::getCart();
    unset($c[$bookId]);
    self::storeCart($c);
  }

  /**
   * empty the shopping cart
   * 
   * @return null
   */
  public static function clear() {
    self::storeCart(array());
  }

  /**
   * check if an item is in the shopping cart
   * 
   * @param integer $bookId book id
   * @return boolean
   */
  public static function contains($bookId) {
    $c = self::getCart();
    return array_key_exists($bookId, $c);
  }

  /**
   * get number of shopping cart items
   * 
   * @return integer
   */
  public static function size() {
    return sizeof(self::getCart());
  }

  /**
   * get the shopping cart contents
   * 
   * @return ShoppingCart object | empty array
   */
  public static function getAll() {
    return self::getCart();
  }

  /**
   * add an item to the shopping cart
   * 
   * @return ShoppingCart object | empty array
   */
  private static function getCart() {
    return isset($_SESSION['cart']) ? $_SESSION['cart'] : array();
  }

  /**
   * make shopping cart persistent
   * 
   * @return null
   */
  private static function storeCart(array $cart) {
    $_SESSION['cart'] = $cart;
  }

}