php的变量引用详解

 1 <?php
 2 class SimpleClass
 3 {
 4     // property declaration
 5     public $var = 'a default value';
 6 
 7     // method declaration
 8     public function displayVar() {
 9         echo $this->var;
10     }
11 }
12 
13 
14 
15 $instance = new SimpleClass();
16 
17 $assigned   =  $instance;
18 $reference  =& $instance;
19 
20 $assigned->var = "aaaaaaa";
21 
22 $assigned = null;
23 
24 var_dump($instance);
25 var_dump($reference);
26 var_dump($assigned);
27 
28 
29 /*
30  输出内容:
31  E:php>php TestClass.php
32 class SimpleClass#1 (1) {
33   public $var =>
34   string(7) "aaaaaaa"
35 }
36 class SimpleClass#1 (1) {
37   public $var =>
38   string(7) "aaaaaaa"
39 }
40 NULL
41 
42 总结:
43 $assigned, $reference, $assigned三个变量引用的都是同一块内存地址，
44 $assigned = null; 之后，断开了指向$assigned的指针,所以$assigned为空，其他的变量不变
45  /