有没有办法在不知道深度的情况下遍历多维数组? [英] Is there a way to loop through a multidimensional array without knowing it's depth?

问题描述

到目前为止，如果我必须遍历一个多维数组，我会为每个维度使用一个 foreach 循环.

So far, if I have to loop through a multidimensional array, I use a foreach loop for each dimension.

例如二维

foreach($array as $key=>$value)
{
    foreach($value as $k2=>$v2)
    {
         echo
    }
}

不知道数组的深度怎么办?即深度是可变的.

What do I do when I don't know the depth of the array? ie the depth is variable.

我唯一能想到的就是编写一整堆循环代码，如果下一个值不是数组就中断循环.这看起来有点傻.

The only thing I can think of is to code a whole stack of loops and to break the loop if the next value is not an array.This seems a little silly.

有更好的方法吗?

推荐答案

是的，您可以使用 递归.这是一个输出数组中所有元素的示例:

Yes, you can use recursion. Here's an example where you output all the elements in an array:

function printAll($a) {
  if (!is_array($a)) {
    echo $a, ' ';
    return;
  }

  foreach($a as $v) {
    printAll($v);
  }
}

$array = array('hello',
               array('world',
                     '!',
                     array('whats'),
                     'up'),
               array('?'));
printAll($array);

在进行递归时，您应该始终记住的是，您需要一个基本情况，这样您就不会再深入了.

What you should always remember when doing recursion is that you need a base case where you won't go any deeper.

我喜欢在继续函数之前检查基本情况.这是一个常见的习语，但不是绝对必要的.如果您应该输出或执行递归调用，您也可以在 foreach 循环中检查，但我经常发现这样的代码更难维护.

I like to check for the base case before continuing the function. That's a common idiom, but is not strictly necessary. You can just as well check in the foreach loop if you should output or do a recursive call, but I often find the code to be harder to maintain that way.

当前输入与基本情况之间的距离"称为变体，并且是一个整数.在每次递归调用中，变体都应该严格减少.前面例子中的变体是$a 的深度.如果您不考虑变体，您可能会面临无限递归的风险，最终脚本将因 而死亡堆栈溢出.在递归函数之前准确记录注释中的变体的情况并不少见.

The "distance" between your current input and the base case is called a variant and is an integer. The variant should be strictly decreasing in every recursive call. The variant in the previous example is the depth of $a. If you don't think about the variant you risk ending up with infinite recursions and eventually the script will die due to a stack overflow. It's not uncommon to document exactly what the variant is in a comment before recursive functions.

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