如何将嵌套数组各层级提取为带指定键值对的独立数组？

我有一个4级嵌套数组，每一层代表组织中的一个层级。每一层的键为层级值，内部包含该层级在数组中的id。最后一层仅为值-id对：

$data =  [
    "top_level_data1" => [ 
            'top_level_id' => 0,           
            'sub_level_1' => [ 
                    'sub_level_1_id' => 0,                       
                    'sub_level_2_data1' => [
                            'sub_level_2_id' => 0,
                            'sub_level_2_data' => [
                                      0 => "some_val",
                                      1 => "some_other_val"
                                 ]
                        ]
              ]
        ],
    "top_level_data2" => [  
            'level_1_id' => 1,            
            'sub_level_1_other' => [      
                    'sub_level_1_id' => 1,              
                    'sub_level_2_data2' => [
                            'sub_level_2_id' => 1,
                            'sub_level_3_data1' => [
                                      2 => "another_val",
                                      3 => "bar",
                                      4 => "foo"
                                 ]
                        ],
                    'sub_level_2_data3' => [
                            'sub_level_2_id' => 2,
                            'sub_level_3_data2' => [
                                      5 => "foobar",
                                      6 => "hello",
                                      7 => "goodbye"
                                 ]
                        ]
              ]
        ] 
];

我希望将其提取为包含层级值-id对的独立数组。上述示例的预期输出（不含上层id）：

$top_level = [
     0 => "top_level_data1",
     1 => "top_level_data2"
];

$sub_level_1 = [
    0 => "sub_level_1",
    1 => "sub_level_1_other"
];

$sub_level_2 = [
    0 => "sub_level_2_data1",
    1 => "sub_level_2_data2",
    2 => "sub_level_2_data3"
];

$sub_level_3 = [
    0 => "some_val",
    1 => "some_other_val",
    2 => "another_val",
    3 => "bar",
    4 => "foo",
    5 => "foobar",
    6 => "hello",
    7 => "goodbye"
];

我尝试使用RecursiveIterator但未能成功（起初只想用它验证迭代是否正确，还未按需求分配键值，但结果不符合预期）：

$it = new RecursiveIteratorIterator(new RecursiveArrayIterator($data));
foreach($it as $key => $val) {
    $level[$it->getDepth()][] = $val;
}

可以通过嵌套循环逐层遍历数组，根据层级的id键特征分类收集数据，代码如下：

<?php
$data = [
    "top_level_data1" => [ 
            'top_level_id' => 0,           
            'sub_level_1' => [ 
                    'sub_level_1_id' => 0,                       
                    'sub_level_2_data1' => [
                            'sub_level_2_id' => 0,
                            'sub_level_2_data' => [
                                      0 => "some_val",
                                      1 => "some_other_val"
                                 ]
                        ]
              ]
        ],
    "top_level_data2" => [  
            'level_1_id' => 1,            
            'sub_level_1_other' => [      
                    'sub_level_1_id' => 1,              
                    'sub_level_2_data2' => [
                            'sub_level_2_id' => 1,
                            'sub_level_3_data1' => [
                                      2 => "another_val",
                                      3 => "bar",
                                      4 => "foo"
                                 ]
                        ],
                    'sub_level_2_data3' => [
                            'sub_level_2_id' => 2,
                            'sub_level_3_data2' => [
                                      5 => "foobar",
                                      6 => "hello",
                                      7 => "goodbye"
                                 ]
                        ]
              ]
        ] 
];

// 初始化各层级结果数组
$top_level = [];
$sub_level_1 = [];
$sub_level_2 = [];
$sub_level_3 = [];

// 遍历顶层数据
foreach ($data as $name => $top_item) {
    // 提取顶层id，兼容不同键名
    $id = $top_item['top_level_id'] ?? $top_item['level_1_id'];
    $top_level[$id] = $name;

    // 遍历一级子层
    foreach ($top_item as $sub1_name => $sub1_item) {
        // 跳过id键，只处理子层级数组
        if (str_ends_with($sub1_name, '_id')) continue;
        
        $sub1_id = $sub1_item['sub_level_1_id'];
        $sub_level_1[$sub1_id] = $sub1_name;

        // 遍历二级子层
        foreach ($sub1_item as $sub2_name => $sub2_item) {
            if (str_ends_with($sub2_name, '_id')) continue;
            
            $sub2_id = $sub2_item['sub_level_2_id'];
            $sub_level_2[$sub2_id] = $sub2_name;

            // 遍历三级子层（最后一层）
            foreach ($sub2_item as $sub3_key => $sub3_val) {
                if (str_ends_with($sub3_key, '_id')) continue;
                // 直接合并最后一层的键值对
                $sub_level_3 = array_merge($sub_level_3, $sub3_val);
            }
        }
    }
}

// 输出验证结果
print_r($top_level);
print_r($sub_level_1);
print_r($sub_level_2);
print_r($sub_level_3);
?>

逻辑说明 #

1. 层级过滤：每一层遍历都跳过以_id结尾的键，只处理包含子层级的数组项
2. id兼容：针对顶层不同的id键名（top_level_id/level_1_id）使用空合并运算符做兼容处理
3. 最后一层处理：直接将最内层的键值对合并到结果数组，无需额外转换

内容的提问来源于stack exchange，提问作者pileup