1 
      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.php32 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 NULL41 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  /