Could someone give a perfect example of a basic "user" object system, using PDO?

Question

What I'd like is to see the ideal framework for a system which has a group of objects (ie User) whereby the data is contained in a database. I've been advised to have a User class and a UserMapper class and this is my understanding of how it should look:

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, $email, $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();
?>

But this seems a bit messy in terms of the main.php side. Can I not make one PDO object and have that defined in all of my scripts? As well as a UserMapper object? Or do every time I want to get a user from the database do I need to make a NEW userMapper object, then do findByUserId (as above). Or is there a simpler way to doing this?

If I wanted to call a UserGroup object within the class User, how would I do this? (This would also need to connect to the database through PDO). To do the following seems messy:

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

Answer 1

one thing that i can think of is making this class a singleton, and create the $user above the declaration of the class, so whenever you include this class you'll have that user object.