如何用递归将含父子关系、标量数据不一致的多维数组转为扁平化二维数组

原代码的问题 #

1. 参数传递错误：$i和$branch采用值传递，递归调用时内部修改的是参数副本，无法同步到外层，导致数组元素索引混乱、子节点结果丢失
2. 字段处理不兼容：硬编码取title字段，未处理示例中存在的identifier特殊字段（如id为5556的元素）

修正后的代码 #

function flattenTree(array $elements)
{
    $result = [];
    foreach ($elements as $element) {
        // 提取核心字段，兼容title和identifier两种标题字段
        $item = ['id' => $element['id']];
        if (isset($element['title'])) {
            $item['title'] = $element['title'];
        } elseif (isset($element['identifier'])) {
            $item['identifier'] = $element['identifier'];
        }
        $result[] = $item;
        
        // 递归处理子节点，合并结果到主数组
        if (!empty($element['children'])) {
            $result = array_merge($result, flattenTree($element['children']));
        }
    }
    return $result;
}

// 调用示例
$tree = [
    'children' => [
        [
            'id' => 123,
            'title' => 'test',
            'children' => [
                [
                    'id' => 345,
                    'title' => 'test 1',
                    'children' => [],
                ],
                [
                    'id' => 567,
                    'title' => 'test 2',
                    'children' => [
                        [
                            'id' => 789,
                            'title' => 'test 3',
                            'children' => [],
                        ],
                        [
                            'id' => 333,
                            'title' => 'tset 4',
                            'children' => [
                                [
                                    'id' => 222,
                                    'title' => 'test 5',
                                    'children' => [],
                                ],
                                [
                                    'id' => 111,
                                    'title' => 'test 55',
                                    'children' => [],
                                ],
                                [
                                    'id' => 444,
                                    'title' => 'test 556',
                                    'children' => [],
                                ],
                                [
                                    'id' => 666,
                                    'title' => 'test44',
                                    'children' => [],
                                ],
                            ],
                        ],
                        [
                            'id' => '5556',
                            'identifier' => 'test 2',
                            'children' => [
                                [
                                    'id' => 888,
                                    'title' => 'test 2',
                                    'children' => [],
                                ],
                                [
                                    'id' => 255,
                                    'title' => 'tset',
                                    'children' => [],
                                ],
                                [
                                    'id' => 454,
                                    'title' => 'warm-up-5837',
                                    'children' => [],
                                ],
                            ],
                        ],
                    ],
                ],
            ],
        ],
    ],
];

$result = flattenTree($tree['children']);
print_r($result);

代码说明 #

• 移除冗余的$i索引参数，直接用$result[]追加元素，避免索引混乱
• 通过array_merge合并递归处理的子节点结果，确保所有层级元素都被收集
• 增加字段兼容逻辑，自动识别title或identifier字段，适配示例中的特殊元素
• 调用时需传入根节点的children数组，匹配原树形结构的顶层格式

执行后将得到与预期一致的扁平化二维数组，元素顺序与树形结构的深度优先遍历顺序一致。

内容的提问来源于stack exchange，提问作者Bhumi Shah