php – 有人可以使用PDO给出基本“用户”对象系统的完美示例吗？

user.class.php

/* The class for constructing any user's information
 */

    class User {

        protected $userId,$email,$userGroup;

        protected function getEmail() {
            return $this->email;
        }

        protected function getUserId() {
            return $this->userId;
        }


        public function __construct($userId,$userGroup) {
            $this->userId = $userId;
            $this->email = $email;
            $this->userGroup = $userGroup;
        }

    }

    class UserMapper {
        // database connection
        private $db;

        public function __construct($db)
        {
            $this->db = $db;
        }

        public function findByUserId ($userId) {
            $userObject = new User();
            $q = $this->db->prepare("SELECT userId,email,userGroup FROM user WHERE userId = :userId");
            $q->bindValue(":userId",$id);
            $q->setFetchMode( PDO::FETCH_INTO,$userObject);
            $q->execute();
            $q->fetch(PDO::FETCH_INTO);
            return $userObject;

        }
    }   
?>

main.php

<?php  
    include user.class.php;
    $dbh = new PDO('mysql:host=localhost;dbname=test',$user,$pass,array(PDO::ATTR_PERSISTENT => true));
    $getUser = new UserMapper($dbh);
    $user = $getUser->findByUserId(41);
    echo $user->getEmail();
?>

但就main.php而言,这似乎有些混乱.我可以不制作一个PDO对象并在我的所有脚本中定义了这个对象吗？和UserMapper对象一样？或者每当我想从数据库中获取用户时,我是否需要创建一个新的userMapper对象,然后执行findByUserId(如上所述).或者有更简单的方法吗？

如果我想在User类中调用UserGroup对象,我该怎么做？ (这也需要通过PDO连接到数据库).要做到以下几乎看起来很乱：

<?php
       $dbh = new PDO('mysql:host=localhost;dbname=test',array(PDO::ATTR_PERSISTENT => true));
        $getUserGroup = new UserGroupMapper($dbh);
        $userGroup = $getUserGroupMapper->findByUserId($this->userGroup);
?>