";		if(isset($this->$property_name)){			return ($this->$property_name);		}else		    return (null);	}	private function __set($proeprty, $val)	{		echo "直接设置私有属性的时候，自动调用__set
";        $this->$proeprty = $val;	}	private function __isset($name)	{		echo "isset()函数测试私有成员时，自动调用
";		return isset($this->$name);	}	private function __unset($name)	{		echo "unset()删除私有成员时自动调用
";		unset($this->$name);	}}$p1 = new Person();$p1->name = "xlc";$p1->sex = '男';$p1->age = 22;echo $p1->name;echo $p1->sex;echo $p1->age;isset($p1->name);unset($p1->name);?>