<?php
    /**
     * 针对类中的魔术方法 __isset() 和 __unset() 的例子
     */

class Example {
    public $public;
    protected $protected;
    private $private;
   
    public function __construct(){
        $this->public = 'pub';
        $this->protected = 'pro';
        $this->private = 'pri';
    }
   
    public function __isset($var){
        echo '这里通过__isset()方法查看属性名为 '.$var."\n";
    }
   
    public function __unset($var){
        echo '这里通过__unset()方法要销毁属性名为 '.$var."\n";
    }
}

$exa = new Example;

echo '<pre>';
var_dump(isset($exa->public));
echo "\n";
var_dump(isset($exa->protected));
echo "\n";
var_dump(isset($exa->private));
echo "\n";
var_dump(isset($exa->noVar));
echo "\n";
echo '<hr/>';

unset($exa->public);
var_dump($exa);

echo "\n";
unset($exa->protected);
echo "\n";
unset($exa->private);
echo "\n";
unset($exa->noVar);
echo "\n";

object(Example)#1 (2) {
  ["protected:protected"]=>
  string(3) "pro"
  ["private:private"]=>
  string(3) "pri"
}