PHP树依赖列表仅适用于某些儿童

如何解决PHP树依赖列表仅适用于某些儿童

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

但是我希望父母只提供一些身份证。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。

然后给我类似的东西：

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，在它们之下什么也不要。

要继续，我想要的内容与链接的帖子完全相同，但是我最小的叶子应该只是数组[2,4,5]中存在的叶子的ID

我不知道有人能理解我的问题...

非常感谢

编辑：我已经更新并添加了ID = 5的示例。

解决方法

是的，您的问题很清楚。您只想从底部到顶部重新创建树，仅用于特定叶子的ID。

您可以通过从初始数组中过滤掉所有不必要的类别，然后使用先前找到的功能来构建树来实现。

//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,"title" => "Another Parent Page"],["id" => 5,"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[$id]["parent_id"],$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:
 * [ 1,2,5 ]
 */

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