class danli{	//需要一个保存类的唯一实例的静态成员变量	private static $_instance;	private function __construct(){		echo ‘单例！‘;	}	//创建__clone方法防止对象被复制克隆	public function __clone(){		trigger_error(‘不能被克隆！‘,E_USER_ERROR);	}		//单例方法,用于访问实例的公共的静态方法	public static function getInstance(){		if(!(self::$_instance instanceof self)){			self::$_instance = new self;		}		return self::$_instance;	}		public function test(){		echo ‘调用方法成功‘;	}}$danli = Danli::getInstance();$danli->test();