PHP 싱글톤 및 팩토리 패턴

<?php
interface persion{
  public function say();
}

class man implements persion{
  public function say(){
     echo &#39;i am man&#39;;
  }
}

class factory{
  public static function createman(){
    return new man();
  }
}
$obj = factory::createman();
$obj->say();

<?php
class Database
{
    // 声明$instance为私有静态类型，用于保存当前类实例化后的对象
    private static $instance = null;
    // 数据库连接句柄
    private $db = null;

    // 构造方法声明为私有方法，禁止外部程序使用new实例化，只能在内部new
    private function __construct($config = array())
    {
        $dsn = sprintf(&#39;mysql:host=%s;dbname=%s&#39;, $config[&#39;db_host&#39;], $config[&#39;db_name&#39;]);
        $this->db = new PDO($dsn, $config[&#39;db_user&#39;], $config[&#39;db_pass&#39;]);
    }

    // 这是获取当前类对象的唯一方式
    public static function getInstance($config = array())
    {
        // 检查对象是否已经存在，不存在则实例化后保存到$instance属性
        if(self::$instance == null) {
            self::$instance = new self($config);
        }
        return self::$instance;
   }

    // 获取数据库句柄方法
    public function db()
    {
        return $this->db;
    }

    // 声明成私有方法，禁止克隆对象
    private function __clone(){}
    // 声明成私有方法，禁止重建对象
    private function __wakeup(){}
}

$config = array(
    &#39;db_name&#39; => &#39;test1&#39;,
    &#39;db_host&#39; => &#39;localhost&#39;,
    &#39;db_user&#39; => &#39;root&#39;,
    &#39;db_pass&#39; => &#39;&#39;
);
//获取数据库连接句柄
$obj = database::getInstance($config);
$db = $obj->db();