php底层变量分析

 <?php

 //数组引用
 $arr = array('a','b','c','d');
 $x = & $arr[1];
 $tmp = $arr;
 $arr[1] = 'e';
 echo $tmp[1];  //e

 //数组指针
 $arr = array('a','b','c','d');
 foreach($arr as $key => $val){
 }
 var_dump(current($arr));  //boolean false

 foreach($arr as $key => $val){
     $arr[$key]=$val;
 }
 var_dump(current($arr)); //b

 /*Array
 (
     [0] => a
     [1] => b
     [2] => c
     [3] => a
 )
 Array
 (
     [0] => a
     [1] => b
     [2] => c
     [3] => b
 )
 Array
 (
     [0] => a
     [1] => b
     [2] => c
     [3] => c
 )
 Array
 (
     [0] => a
     [1] => b
     [2] => c
     [3] => c
 )*/
 foreach($arr as &$v){
 }

 foreach($arr as $v){
     print_r($arr);
 }