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();
}
}