php的變量引用詳解

 <?php
 class SimpleClass
 {
     // property declaration
     public $var = 'a default value';
 
     // method declaration
     public function displayVar() {
         echo $this->var;
     }
 }
 
 
 
 $instance = new SimpleClass();
 
 $assigned   =  $instance;
 $reference  =& $instance;
 
 $assigned->var = "aaaaaaa";
 
 $assigned = null;
 
 var_dump($instance);
 var_dump($reference);
 var_dump($assigned);
 
 
 /*
  輸出內容:
  E:\php>php TestClass.php
 class SimpleClass#1 (1) {
   public $var =>
   string(7) "aaaaaaa"
 }
 class SimpleClass#1 (1) {
   public $var =>
   string(7) "aaaaaaa"
 }
 NULL
 
 總結:
 $assigned, $reference, $assigned三個變量引用的都是同一塊內存地址，
 $assigned = null; 之後，斷開了指向$assigned的指針,所以$assigned為空，其他的變量不變
  /