dedecms实现商城功能的会员价格体系

一次一个人让我给他用dedecms做程序，然后商品的地方需要不同的会员不同的价格，必须登录才能购买，然后找了一下流程文件，自己改了一下 1.首先我们后台商品添加几个字段价格的 我添加是 trueprice 优惠价格 hprice 会员价格 gprcie 高级会员价格 2.然后修改/plus/posttocar.php这个文件的源代码（修改几个地方，给大家讲一下很简单）

require_once (dirname(__FILE__) . "/../include/common.inc.php");
require_once DEDEINC.'/shopcar.class.php';  //购物车的类
require_once DEDEINC.'/memberlogin.class.php'; //会员登录的类
$cfg_ml = new MemberLogin(); //实例化类
if(empty($cfg_ml->M_ID)){  //如果没有登录自动跳转到登录页面
	 ShowMsg("您没有登录！", "/member/login.php", false, 5000);
	 exit;
 }else{
$cart = new MemberShops();

$do = isset($do) ? trim($do) : 'add';

if($do == 'add')
{
    /*
    function addItem();                add a product to car
    */
    $buynum = isset($buynum) && is_numeric($buynum) ? $buynum : 1;
    $id =empty($id)? "" : intval($id);
    $buynum = ($buynum < 1) ? 1 : $buynum;
    $rs = $dsql->GetOne("SELECT id,channel,title FROM #@__archives WHERE id='$id'");
    if(!is_array($rs))
    {
        ShowMsg("该商品已不存在！","-1");
        exit();
    }
	//我们通过userid在会员里边找 rank这个字段 就是等级字段
         $userid = $cfg_ml->M_ID;
	$result=$dsql->Getone("select rank from #@__member where mid='$userid'");
	$dengji=$result[rank];
    $cts = GetChannelTable($rs['channel']);
//这里根据等级值 判断输出哪个价格 这样就结束了
	switch ($dengji)
				{
			case 10:
			  $rows = $dsql->GetOne("SELECT aid as id,trueprice as price,units FROM `$cts[addtable]` WHERE aid='$id'");
			  break;
			case 20:
			  $rows = $dsql->GetOne("SELECT aid as id,hprice as price,units FROM `$cts[addtable]` WHERE aid='$id'");
			  break;
			case 50:
			  $rows = $dsql->GetOne("SELECT aid as id,gprice as price,units FROM `$cts[addtable]` WHERE aid='$id'");
			  break;
			default:
			  echo "您不是会员";
					break;
			}
   
    if(!is_array($rows))
    {
        ShowMsg("该商品已不存在！","-1");
        exit();
    }
    $rows['buynum'] = $buynum;
    $rows['title']     = $rs['title'];
    $cart->addItem($id, $rows);
    ShowMsg("已添加加到购物车,<a href='car.php'>查看购物车</a>","car.php");
    exit();
	
}