php购物车有关问题

<?php<br />
  include ('book_sc_fns.php');<br />
  // The shopping cart needs sessions, so start one<br />
  session_start();<br />
<br />
  @$new = $_GET['new'];<br />
<br />
  if($new) {<br />
    //new item selected<br />
    if(!isset($_SESSION['cart'])) {<br />
      $_SESSION['cart'] = array();<br />
      $_SESSION['items'] = 0;<br />
      $_SESSION['total_price'] ='0.00';<br />
    }<br />
<br />
    if(isset($_SESSION['cart'][$new])) {<br />
      $_SESSION['cart'][$new]++;<br />
    } else {<br />
      $_SESSION['cart'][$new] = 1;<br />
    }<br />
<br />
    $_SESSION['total_price'] = calculate_price($_SESSION['cart']);<br />
    $_SESSION['items'] = calculate_items($_SESSION['cart']);<br />
  }<br />
<br />
  if(isset($_POST['save'])) {<br />
    foreach ($_SESSION['cart'] as $isbn => $qty) {<br />
      if($_POST[$isbn] == '0') {<br />
        unset($_SESSION['cart'][$isbn]);<br />
      } else {<br />
        $_SESSION['cart'][$isbn] = $_POST[$isbn];<br />
      }<br />
    }<br />
<br />
    $_SESSION['total_price'] = calculate_price($_SESSION['cart']);<br />
    $_SESSION['items'] = calculate_items($_SESSION['cart']);<br />
  }<br />
<br />
  do_html_header("Your shopping cart");<br />
<br />
  if(($_SESSION['cart']) && (array_count_values($_SESSION['cart']))) {<br />
    display_cart($_SESSION['cart']);<br />
  } else {<br />
    echo "<p>there are no items in your cart</p>
                    <div class="aritcle_card">
                        <a class="aritcle_card_img" href="/xiazai/code/8856">
                            <img src="https://img.php.cn/upload/webcode/000/000/010/175703400611818.jpg" alt="品杰电子商务购物平台系统">
                        </a>
                        <div class="aritcle_card_info">
                            <a href="/xiazai/code/8856">品杰电子商务购物平台系统</a>
                            <p>网上购物商城，它属于BtoC电子商务网站平台，它能够直接绕过中介（如批发商、销售商或经销商）建立与客户的直接关系。该网站可以为用户提供商品的详细信息，用户可以在线购买商品，确定镇定的订单；同时提供关于商品或电子零销商的选择建议等等。网上购物平台使得人们的购买变的更方便、更加容易。    前台功能模块有：  热销商品   订单管理    购物车    结算中心     注册会员　　 用户登录    </p>
                            <div class="">
                                <img src="/static/images/card_xiazai.png" alt="品杰电子商务购物平台系统">
                                <span>0</span>
                            </div>
                        </div>
                        <a href="/xiazai/code/8856" class="aritcle_card_btn">
                            <span>查看详情</span>
                            <img src="/static/images/cardxiayige-3.png" alt="品杰电子商务购物平台系统">
                        </a>
                    </div>
                <hr/>";<br />
  }<br />
<br />
  $target = "index.php";<br />
<br />
  // if we have just added an item to the cart, continue shopping in that category<br />
  if($new)   {<br />
    $details =  get_book_details($new);<br />
    if($details['catid']) {<br />
      $target = "show_cat.php?catid=".$details['catid'];<br />
    }<br />
  }<br />
  display_button($target, "continue-shopping", "Continue Shopping");<br />
<br />
  // use this if SSL is set up<br />
  // $path = $_SERVER['PHP_SELF'];<br />
  // $server = $_SERVER['SERVER_NAME'];<br />
  // $path = str_replace('show_cart.php', '', $path);<br />
  // display_button("https://".$server.$path."checkout.php",<br />
  //                 "go-to-checkout", "Go To Checkout");<br />
<br />
  // if no SSL use below code<br />
  display_button("checkout.php", "go-to-checkout", "Go To Checkout");<br />
<br />
  do_html_footer();<br />
?><br />