Magic method __unset __isset __destruct

__unset Trigger timing: the destruction of objects in the external private or protected member properties when calling

　　　　This method has one parameter: parameter is the name of the private property of members of the

__isset Trigger timing: determining an object in an external private or protected member properties when calling

　　　　This method has one parameter, the parameter is a member of the private property name

__destruct destructor   

　　　　Trigger timing: when the object is destroyed automatically call

<?php

    class Person
    {
        public $name;
        protected $age;
        private $height;

        public function __unset($name){
            if($name == 'age'){
                unset($this->age);
            }
        }

        public function __set($name,$value){
            if($name == 'age'){
                $this->$name = $value;
            }
        }

        public function __get($name){
            if($name == 'age'){
                return $this->$name;
            }
        }

        public function  __isset($name){
            if($name == 'age'){
                isset return (the this $ -> $ name); 
            } 
        } 

        public __destruct function () { 
            echo 'I'm going for a walk! '; 
    } 
    } 

    $ = New new NIU the Person (); 
    // the unset ($ niu-> Age); 
    $ niu-> Age = 100; 
    // echo $ niu-> Age; 

    var_dump (isset ($ niu-> Age) );