在多维数组上使用 UASORT 的 PHP 递归循环

Question

我正在编写一个循环遍历多维数组的脚本，它按预期工作（有点），但我遇到了无法纠正的错误。

我仍然不太习惯构建循环来管理嵌套数组。

这是我的代码。目标是按 sequence 键的值对每一层进行排序，最后我将数组导出为 json。

序列键可能存在也可能不存在于每个子数组中，因此可能需要某种 if 子句

<?php
$list = [
        "key" => "book",
        "sequence" => 1,
        "items" => [
            [
                "key" => "verse",
                "sequence" => 2,
                "items" => [
                    ["sequence" => 3],
                    ["sequence" => 1],
                    ["sequence" => 2],
                ],
            ],
            [
                "key" => "page",
                "sequence" => 1,
                "items" => [
                    [
                        "key" => "page",
                        "sequence" => 2,
                        "items" => [
                            ["sequence" => 2],
                            ["sequence" => 1],
                            ["sequence" => 3],
                        ],
                    ],
                    [
                        "key" => "paragraph",
                        "sequence" => 1,
                        "items" => [
                            ["sequence" => 2],
                            ["sequence" => 1],
                            ["sequence" => 3],
                        ],
                    ],
                ],
            ],
        ],
    ];

function sortit(&$array){

    foreach($array as $key => &$value){
        //If $value is an array.
        if(is_array($value)){

            if($key == "items"){
                uasort($value, function($a,&$b) {
                   return $a["sequence"] <=> $b["sequence"];
                });

            }
            //We need to loop through it.
            sortit($value);
        } else{
            //It is not an array, so print it out.
            echo $key . " : " . $value . "<br/>";
        }
    }
}


sortit($list);

echo "<pre>";

print_r($list);

?>

这是我得到的输出和错误，我想我理解为什么会抛出错误，但同时我无法执行修复错误所需的适当检查。

key : book
sequence : 1
key : page
sequence : 1

E_WARNING : type 2 -- Illegal string offset 'sequence' -- at line 39

E_NOTICE : type 8 -- Undefined index: sequence -- at line 39
sequence : 1
sequence : 2
sequence : 3
sequence : 1
key : page

E_WARNING : type 2 -- Illegal string offset 'sequence' -- at line 39

E_NOTICE : type 8 -- Undefined index: sequence -- at line 39
sequence : 1
sequence : 2
sequence : 3
sequence : 2
key : verse

并不是我很担心，但我想要的另一件事是数组仍按原始顺序构造，即：key, sequence, items

Answer 1

使用usort 和数组引用使其变得简单。如果我们正在处理具有集合 item 键的数组，则对 item 数组进行排序并递归其子节点，否则，我们位于叶节点并且可以返回。

function seqSort(&$arr) {
    if (is_array($arr) && array_key_exists("items", $arr)) {
        usort($arr["items"], function ($a, $b) {
            return $a["sequence"] - $b["sequence"];
        });

        foreach ($arr["items"] as &$item) {
            $item = seqSort($item);
        }
    }

    return $arr;
}

结果：

array (
  'key' => 'book',
  'sequence' => 1,
  'items' => 
  array (
    0 => 
    array (
      'key' => 'page',
      'sequence' => 1,
      'items' => 
      array (
        0 => 
        array (
          'key' => 'page',
          'sequence' => 1,
          'items' => 
          array (
            0 => 
            array (
              'sequence' => 1,
            ),
            1 => 
            array (
              'sequence' => 2,
            ),
            2 => 
            array (
              'sequence' => 3,
            ),
          ),
        ),
      ),
    ),
    1 => 
    array (
      'key' => 'verse',
      'sequence' => 2,
      'items' => 
      array (
        0 => 
        array (
          'sequence' => 1,
        ),
        1 => 
        array (
          'sequence' => 2,
        ),
        2 => 
        array (
          'sequence' => 3,
        ),
      ),
    ),
  ),
)

Try it!

请注意，最外面的结构是一个根节点，它不是数组的一部分，无法排序（这可能是无意的，会造成混淆）。