How to implement the Data Mapper design pattern in PHP for data persistence?

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class UserMapper {
    private $db;

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

    public function insert(User $user) {
        // Implementation code for inserting user object into database
    }

    public function update(User $user) {
        // Implementation code for updating user object in database
    }

    public function delete(User $user) {
        // Implementation code for deleting user object from database
    }

    public function select($id) {
        // Implementation code for selecting user object from database based on id
    }
}

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class User {
    private $id;
    private $name;
    private $email;

    public function __construct($id, $name, $email) {
        $this->id = $id;
        $this->name = $name;
        $this->email = $email;
    }

    public function getId() {
        return $this->id;
    }

    public function getName() {
        return $this->name;
    }

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

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$db = new PDO('mysql:host=localhost;dbname=mydatabase', 'username', 'password');
$mapper = new UserMapper($db);

// Create a new user
$user = new User(null, 'John Doe', '[email protected]');
$mapper->insert($user);

// Update an existing user
$user = $mapper->select(1);
$user->setName('Jane Doe');
$mapper->update($user);

// Delete a user
$user = $mapper->select(2);
$mapper->delete($user);