php:对象运行时新增成员变量

 1 <?php
 2 class PropertyTest {
 3      /**  被重载的数据保存在此  */
 4     private $data = array();
 5 
 6  
 7      /**  重载不能被用在已经定义的属性  */
 8     public $declared = 1;
 9 
10      /**  只有从类外部访问这个属性时，重载才会发生 */
11     private $hidden = 2;
12 
13     public function __set($name, $value) 
14     {
15         echo "Setting '$name' to '$value'\n";
16         $this->data[$name] = $value;
17     }
18 
19     public function __get($name) 
20     {
21         echo "Getting '$name'\n";
22         if (array_key_exists($name, $this->data)) {
23             return $this->data[$name];
24         }
25 
26         $trace = debug_backtrace();
27         trigger_error(
28             'Undefined property via __get(): ' . $name .
29             ' in ' . $trace[0]['file'] .
30             ' on line ' . $trace[0]['line'],
31             E_USER_NOTICE);
32         return null;
33     }
34 
35     public function __isset($name) 
36     {
37         echo "Is '$name' set?\n";
38         return isset($this->data[$name]);
39     }
40 
41     public function __unset($name) 
42     {
43         echo "Unsetting '$name'\n";
44         unset($this->data[$name]);
45     }
46 
47     /**  非魔术方法  */
48     public function getHidden() 
49     {
50         return $this->hidden;
51     }
52 }
53 
54 
55 echo "<pre>\n";
56 
57 $obj = new PropertyTest;
58 
59 $obj->a = 1;
60 echo $obj->a . "\n\n";
61 
62 var_dump(isset($obj->a));
63 unset($obj->a);
64 var_dump(isset($obj->a));
65 echo "\n";
66 
67 echo $obj->declared . "\n\n";
68 
69 echo "Let's experiment with the private property named 'hidden':\n";
70 echo "Privates are visible inside the class, so __get() not used...\n";
71 echo $obj->getHidden() . "\n";
72 echo "Privates not visible outside of class, so __get() is used...\n";
73 echo $obj->hidden . "\n";
74 ?>