PHP flat array to multi-dimensional array by parent keys?

Question

How can I turn this flat array into a multi-dimensional array according to the matched key?

$items = [
    0 => [
        'id' => 100,
        'parent' => 0,
        'url' => 'Home'
    ],

    1 => [
        'id' => 101,
        'parent' => 0,
        'url' => 'About'
    ],

    2 => [
        'id' => 102,
        'parent' => 101,
        'url' => 'Group'
    ],

    3 => [
        'id' => 103,
        'parent' => 102,
        'url' => 'Mission'
    ],
    4 => [
        'id' => 104,
        'parent' => 102,
        'url' => 'Vision'
    ],
];

My attempt:

$new_items = array();
foreach ($items as $key => $item) {

    // Store what you need.
    $temp_item = array(
        'id' => $item['id'],
        'url' => $item['url'],
        'parent_id' => $item['parent'],
        'children' => array()
    );

    // Item does not have a parent so item_parent equals 0 (false).
    if (!$item['parent']) {
        // Push the item to the array.
        array_push($new_items, $temp_item);
    }

    // Item that has a parent.
    if ($item['parent']) {

        // Search key by column 'id'.
        $key = array_search($item['parent'], array_column($new_items, 'id'));

        // Push sub item to the children array.
        array_push($new_items[$key]['children'], $temp_item);
    }
}

print_r($new_items);

Result:

Array
(
    [0] => Array
        (
            [id] => 100
            [url] => Home
            [parent_id] => 0
            [children] => Array
                (
                    [0] => Array
                        (
                            [id] => 103
                            [url] => Mission
                            [parent_id] => 102
                            [children] => Array
                                (
                                )

                        )

                    [1] => Array
                        (
                            [id] => 104
                            [url] => Vision
                            [parent_id] => 102
                            [children] => Array
                                (
                                )

                        )

                )

        )

    [1] => Array
        (
            [id] => 101
            [url] => About
            [parent_id] => 0
            [children] => Array
                (
                    [0] => Array
                        (
                            [id] => 102
                            [url] => Group
                            [parent_id] => 101
                            [children] => Array
                                (
                                )

                        )

                )

        )

)

This is what I am after:

Array
(
    [0] => Array
        (
            [id] => 100
            [url] => Home
            [parent_id] => 0
            [children] => Array
                (
                )

        )

    [1] => Array
        (
            [id] => 101
            [url] => About
            [parent_id] => 0
            [children] => Array
                (
                    [0] => Array
                        (
                            [id] => 102
                            [url] => Group
                            [parent_id] => 101
                            [children] => Array
                                (
                                    [0] => Array
                                        (
                                            [id] => 103
                                            [url] => Mission
                                            [parent_id] => 102
                                            [children] => Array
                                                (
                                                )

                                        )

                                    [1] => Array
                                        (
                                            [id] => 104
                                            [url] => Vision
                                            [parent_id] => 102
                                            [children] => Array
                                                (
                                                )

                                        )
                                )

                        )

                )

        )

)

Any ideas and suggestions?

Rahul · Accepted Answer · 2017-12-22 09:02:57Z

2

From link

I have changed function parameters as per requirement.
Here is your code.

function buildTree(array $elements, $options = [
    'parent_id_column_name' => 'parent',
    'children_key_name' => 'children',
    'id_column_name' => 'id'], $parentId = 0)
    {
    $branch = array();
    foreach ($elements as $element) {
        if ($element[$options['parent_id_column_name']] == $parentId) {
            $children = buildTree($elements, $options, $element[$options['id_column_name']]);
            if ($children) {
                $element[$options['children_key_name']] = $children;
            }else{
                $element[$options['children_key_name']] = []; // added this line for empty children array
            }
            $branch[] = $element;
        }
    }
    return $branch;
}

Here is your working demo.

answered Dec 22, 2017 at 9:02

Rahul

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1 Comment

Rahul Over a year ago

It is optimized but yeah robust with n-levels

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