PHP 树依赖列表仅适用于某些子项

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 togenerate multiDimensional array from database result但我想要父母只需要一些身份证。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。并返回给我这样的东西：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，并且没有低于他们的孩子。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中存在的叶子的 id [2,4,5]不知道有没有人明白我的问题...

Answer 1

是的，你的问题很清楚。您想要从下到上重新创建树，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);