php 设计模式（数据库对象模式）

/** * 数据对象映射莫使，就是将对象和数据存储映射起来，对一个对象的操作就是对数据库的操作 */interface Database{    public function connect($host, $name, $password, $db);    public function query($sql);    public function close();}class MYSQLI implements Database{    protected $conn;    public function connect($host, $name, $password, $db)    {        $this->conn = mysqli_connect($host, $name, $password, $db);    }    public function query($sql)    {        return mysqli_query($this->conn,$sql);    }    public function close()    {        mysqli_close($this->conn);    }}class User{    protected $data;    protected $db;    public function __construct($id){        $this->db = new MYSQLI('127.0.0.1','admin','admin','oo');        $res = $this->db->query('select * from user where id = '.$id);        $this->data = $res->fetch_assoc();    }    protected function __set($key,$value){        $this->data[$key] = $value;    }    protected function __get($key){        $this->$key = $this->data[$key];    }    public function save(){        $key = array_keys($this->data);        $value = array_values($this->data);        $sql = 'update user set () '.$key.' values '.$value.' where id = '.$this->id;        if($this->db->query($sql)){            echo 'ok';        }    }    protected function __destruct(){        $this->db->close();    }}