PHP树依赖列表仅适用于某些孩子

Question

我正在寻找一个可以创建分层数组但仅适用于某些孩子的函数。

这个例子似乎不错： Recursive function to generate multidimensional array from database result

但我想要父母只是为了一些 ID。例如：

+-------+---------------+---------------------------+
|   id  |   parent_id   |           title           |
+-------+---------------+---------------------------+
|   1   |       0       |   Parent Page             |
|   2   |       1       |   Sub Page                |
|   3   |       2       |   Sub Sub Page            |
|   4   |       0       |   Another Parent Page     |
|   5   |       1       |   Sub Page 2              |
+-------+---------------+---------------------------+

我只想要 id 2、4 和 5 的层次结构。

然后给我这样的东西：

Array
(
    [0] => Array
        (
            [id] => 1
            [parent_id] => 0
            [title] => Parent Page
            [children] => Array
                        (
                            [0] => Array
                                (
                                    [id] => 2
                                    [parent_id] => 1
                                    [title] => Sub Page                                                    
                                ),
                            [1] => Array
                                (
                                    [id] => 5
                                    [parent_id] => 1
                                    [title] => Sub Page 2                                                     
                                )
                        )
        )
    [1] => Array
        (
            [id] => 4
            [parent_id] => 0
            [title] => Another Parent Page
        )
)

2、4 和 5 应该是最小的孩子，它们下面没有任何东西。

继续，我想要的与链接的帖子完全相同，但我最小的叶子应该只是数组 [2,4,5] 中存在的叶子 id

不知道有没有人理解我的问题...

非常感谢

编辑：我更新并添加了 id = 5 的示例。

Answer 1

是的，你的问题很清楚。您想从底部到顶部重新创建树，仅针对特定叶子的 id。

您可以通过从初始数组中过滤掉所有不必要的类别来实现它，然后使用您之前找到的函数构建树。

//Assuming you have this array with mysql result of all possible categories
$mysqlRows = [
    ["id" => 1, "parent_id" => 0, "title" => "Parent Page"],
    ["id" => 2, "parent_id" => 1, "title" => "Sub Page"],
    ["id" => 3, "parent_id" => 2, "title" => "Sub Sub Page"],
    ["id" => 4, "parent_id" => 0, "title" => "Another Parent Page"],
    ["id" => 5, "parent_id" => 1, "title" => "Sub Page 2"]
];

/*
 * Fill $participatingIds array with id of categories that related to our needs
 * Be aware that $participatingIds has & sign - it means
 * that it will be passed by reference
 */
function collectAllParentsId($id, $mysqlRows, &$participatingIds)
{
    if (!in_array($id, $participatingIds)) {
        $participatingIds[] = $id;
    }
    if ($mysqlRows[$id]["parent_id"] !== 0) {
        collectAllParentsId($mysqlRows[$id]["parent_id"], $mysqlRows, $participatingIds);
    }
}

//Initial function to build a tree from a flat category array
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;
}


/* START */

/*
 * Make array indexes equals to the category's "id",
 * so we can access category like this $mysqlRows[$category_id]
*/
$mysqlRows = array_column($mysqlRows, null, "id");

//Array of ids for which you want create a tree
$someIds = [2, 4, 5];

/*
 * Create one flat array with all Ids that will participating in the tree
 * (leaf id and all of it parents id)
 * Order of ids is doesn't matter here
 * $ids will looks like this:
 * [ 1, 2, 4, 5 ]
 */

$ids = [];
foreach ($someIds as $id) {
    collectAllParentsId($id, $mysqlRows, $ids);
}

//Now filter out all categories that doesn't participating in out tree
$filteredRows = array_filter(
    $mysqlRows,
    function ($key) use ($ids) {
        return (in_array($key, $ids));
    },
    ARRAY_FILTER_USE_KEY
);

//Now we have only desired categories - create the tree from it:
$tree = buildTree($filteredRows);

var_dump($tree);