使用 buildTree 生成所有可能分支的数组

Question

我正在使用此处的 buildTree 函数来获取父级的所有子级，但我正在努力调整代码以在树中生成所有可能的分支。

样本数据：

Array
(
    [0] => Array
        (
            [id] => 7
            [parent_id] => 6
        )

    [1] => Array
        (
            [id] => 8
            [parent_id] => 6
        )

    [2] => Array
        (
            [id] => 17
            [parent_id] => 7
        )

    [3] => Array
        (
            [id] => 18
            [parent_id] => 7
        )

    [4] => Array
        (
            [id] => 20
            [parent_id] => 17
        )

    [5] => Array
        (
            [id] => 21
            [parent_id] => 17
        )

    [6] => Array
        (
            [id] => 22
            [parent_id] => 17
        )
)

构建树：

function buildTree(array $elements, $parentId = 0) {
    $branch = array();
    foreach ($elements as $element) {
        if ($element['parent_id'] == $parentId) {
            $children = buildTree($elements, $element['id']);
                if ($children) {
                    $element['children'] = $children;
                }
                $branch[] = $element;
            }
        }
        return $branch;
    }
}

我要输出的内容：

Array
(
    [0] => Array
        (
            6, 7, 17, 20
        )

    [1] => Array
        (
            6, 7, 17, 21
        )

    [2] => Array
        (
            6, 7, 17, 22
        )

    [3] => Array
        (
            6, 7, 18
        )

    [4] => Array
        (
            6, 8
        )
)

我尝试使用 foreach 循环而不是 if($children) 来生成结果数组中的下一个键，并从树的更高层合并现有数据，但没有成功。

非常感谢任何帮助！

Answer 1

好吧，在您的 buildTree 函数中有几个错误。首先，您不能检查数组中不存在的键，例如“parent”（有“parent_id”）。

请检查这是否是您要查找的内容：

<?php

$input =
[
  [
    "id" => 7,
    "parent_id" => 6
  ],
  [
    "id" => 8,
    "parent_id" => 6
  ],
  [
    "id" => 17,
    "parent_id" => 7
  ],
  [
    "id" => 18,
    "parent_id" => 7
  ],
  [
    "id" => 20,
    "parent_id" => 17
  ],
  [
    "id" => 21,
    "parent_id" => 17
  ],
  [
    "id" => 22,
    "parent_id" => 17
  ]
];

function buildTree(array $elements, $parentId = 0)
{
    $branch = array();
    foreach ($elements as $element) {
        if ($element['parent_id'] == $parentId) {
            $children = buildTree($elements, $element['id']);
            if (!empty($children)) {
                $element['children'] = $children;
            }
            $branch[] = $element;
        }
    }
    return $branch;
}

print_r(buildTree($input, 7));