php实现多维数组中每个单元值(数字)翻倍的方法

<?php
$arr = array(1,3,'a'=>20,'b'=>array(2,4,6,'c'=>7));
function arr2($arr){
foreach($arr as $key=>$v){
if(!is_array($v)){
$arr[$key] *= 2;
}else{
$arr[$key] = arr2($arr[$key]);
}
}
return $arr;
}
echo "<pre>";
print_r(arr2($arr));
?>

<?php
$arr = array(1,3,'a'=>20,'b'=>array(2,4,6,'c'=>7));
function t(&$arr){
$arr *= 2;
}
echo "<pre>";
array_walk_recursive($arr,'t');
print_r($arr);
?>