<"mysql:host=$host;dbname=$db", "$user", "$pwd", array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
      $this->pdo->query("set names utf8");
    } catch (PDOException $e) {
      echo $e->getMessage();
    }
  }
  //添加商品到购物车
  public function add_cart($productid, $num)
  {
    $sql = "select price from shop_product where id=";
    $stmt = $this->pdo->prepare($sql);
    $stmt->execute(array($productid));
    $data = $stmt->fetch(PDO::FETCH_ASSOC);
    $price = $data['price'];
    $createtime = time();
    $sql = "select * from shop_cart where productid=";
    $stmt = $this->pdo->prepare($sql);
    $stmt->execute(array($productid, $_SESSION['user_id']));
    $data = $stmt->fetch(PDO::FETCH_ASSOC);
    if ($data) {
      $sql = "update shop_cart set num=num+";
      $params = array($num, $_SESSION['user_id'], $productid);
    } else {
      $sql = "insert into shop_cart(productid,num,userid,price,createtime) values(";
      $params = array($productid, $num, $_SESSION['user_id'], $price, $createtime);
    }
    $stmt = $this->pdo->prepare($sql);
    $stmt->execute($params);
    $rows = $stmt->rowCount();
    return $rows "update shop_cart set num=";
    $stmt = $this->pdo->prepare($sql);
    $stmt->execute(array($num, $_SESSION['user_id'], $productid));
    $rows = $stmt->rowCount();
    return $rows "delete from shop_cart where userid=";
    $stmt = $this->pdo->prepare($sql);
    $this->pdo->execute(array($this->user_id));
    $rows = $stmt->rowCount();
    return $rows "delete from shop_cart where productid=";
    $stmt = $this->pdo->prepare($sql);
    $stmt->execute(array($productid, $_SESSION['user_id']));
    $rows = $stmt->rowCount();
    return $rows "_blank" href="//www.jb51.net/Special/554.htm">PHP+MySQL购物车开发专题》、《php面向对象程序设计入门教程》、《PHP数学运算技巧总结》、《PHP数组(Array)操作技巧大全》、《php字符串(string)用法总结》、《PHP数据结构与算法教程》、《php程序设计算法总结》、《php正则表达式用法总结》、及《php常见数据库操作技巧汇总》

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