如何使用array_walk_recursive取消设置元素 [英] How to unset elements using array_walk_recursive

问题描述

我需要从数组未设置元素嵌套到另一个数组中，只有第一个 N 元素将被保留（ N A途径是predefined）。只有具有数字索引元素都应该受到影响。

I need to unset elements from arrays that are nested into another array, in a way that only the first N elements would be kept (N being predefined). Only elements that have a numerical index should be affected.

输入数组：

Array
(
    [0] => Array (
        [a] => 'w'
        [b] => Array (
             [0]=> 'x'
             [1]=> 'x'
             [2]=> 'x'
        )
    )               
    [1] => Array (
        [a] => 'y'
    )
    [2] => Array (
        [0] => 'z'
        [1] => 'z'
        [2] => 'z'
    )
)

所需的输出（带有 N = 2 ）

Array
(
    [0] => Array (
        [a] => 'w'
        [b] => Array (
             [0]=> 'x'
             [1]=> 'x'
        )
    )               
    [1] => Array (
        [a] => 'y'
    )
)

根据上述定义

，仅 [0] [B] [2] 和 [2] 得到未设置的，因为他们有一个数字指标，因为它们都重新presnted各自阵列的第三元素。

Based on the above definition, only [0][b][2] and [2] got unset because they had a numerical index and because they both represnted the 3rd element of their respective array.

推荐答案

没有测试过，但是这样的事情可能会奏效。

Haven't tested but something like this might work.

function myFunc(&$array){
foreach($array as $key=>&$value){
 if(is_array($value)){
   myFunc($value);
 }
 if(is_numeric($key) && $key > 1){
   unset($array[$key]);
 }
}
}

关于array_walk。 php.net说：

About array_walk. php.net says:

程序员不能添加，设置或
  重新排序的元素。如果回调不
  不尊重这一要求，
  此函数的行为是
  不确定的，和未predictable。

the programmer cannot add, unset or reorder elements. If the callback does not respect this requirement, the behavior of this function is undefined, and unpredictable.

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