How PHP Reference works?

来源：互联网发布：数据库系统实现 epub 编辑：程序博客网时间：2024/06/08 03:33

简单的看一下php reference 是如何工作的 <?php /* 图片为内存变化图 ______________________________ |pointer | value | variable | ----------------------------------- |   1    | NULL |    ---    | |   2    | NULL |    ---    | |   3    | NULL |    ---    | |   4    | NULL |    ---    | |   5    | NULL |    ---    | ------------------------------------ 创建一些变量 */ $a=10; $b=20; $c=array ('one'=>array (1, 2, 3)); /* 查看内存 _______________________________ |pointer | value |    variable's    | ----------------------------------- |   1    | 10    |    $a    | |   2    | 20    |    $b    | |   3    | 1    | $c['one'][0]   | |   4    | 2    | $c['one'][1]   | |   5    | 3    | $c['one'][2]   | ------------------------------------ do */ $a=&$c['one'][2]; /*查看内存
_______________________________ |pointer | value |    variable's    | ----------------------------------- |   1    | NULL |    --- | // $a 的值被销毁并且 pointer free |   2    | 20    |    $b    | |   3    | 1    | $c['one'][0]   | |   4    | 2    | $c['one'][1]   | |   5    | 3    | $c['one'][2] ,$a | // $a现在在这里
------------------------------------ do */ $b=&$a; // "$c['one'][2]" 和 "$a" 为同一pointer. /*查看内存
_________________________________ |pointer | value |    variable's    | -------------------------------------- |   1    | NULL |    --- | |   2    | NULL |    --- | //$b 的值被销毁并且 pointer free |   3    | 1    | $c['one'][0]    | |   4    | 2    | $c['one'][1]    | |   5    | 3    |$c['one'][2] ,$a , $b | // $b 现在在这里 --------------------------------------- next do */ unset($c['one'][2]); /*查看内存
_________________________________ |pointer | value |    variable's    | -------------------------------------- |   1    | NULL |    --- | |   2    | NULL |    --- | |   3    | 1    | $c['one'][0]    | |   4    | 2    | $c['one'][1]    | |   5    | 3    | $a , $b | // $c['one'][2] 被销毁 --------------------------------------- next do   */ $c['one'][2]=500; //now it is in array /*查看内存
_________________________________ |pointer | value |    variable's    | -------------------------------------- |   1    | 500 | $c['one'][2]    | |   2    | NULL |    --- | |   3    | 1    | $c['one'][0]    | |   4    | 2    | $c['one'][1]    | |   5    | 3    | $a , $b | //这个指针正在被使用 --------------------------------------- $c['one'][2]=&$a; unset($a); unset($b);   /*查看内存
_________________________________ |pointer | value |    variable's    | -------------------------------------- |   1    | NULL |    --- | |   2    | NULL |    --- | |   3    | 1    | $c['one'][0]    | |   4    | 2    | $c['one'][1]    | |   5    | 3    | $c['one'][2]    | //$c['one'][2] 被返回, $a,$b 被销毁 --------------------------------------- ?>