--- title: "Arrays" description: "Arr of Derafu Support" type: "docs" category: "doc" tags: [] authors: [Anonymous] date: "2026-10-08" last_update: "2026-10-08" time_minutes: 3 draft: false unlisted: false url: "https://www.derafu.dev/docs/core/support/arrays" --- # Arrays `Arr` has the transformations of arrays that come up again and again: flat and nested forms, casting, trees, tables and subsets. | Method | What it does | | --- | --- | | `Arr::dot($array, $prefix = '')` | Flattens an array into keys with dots. | | `Arr::nested($array)` | The opposite: keys with dots into an array of arrays. | | `Arr::cast($array, $emptyValue = '')` | Casts the values of an array, recursively. | | `Arr::ensureArrayAtPath(&$array, $path)` | Makes sure that the value at a path is a list. | | `Arr::ensureIdInElements($data, $idField)` | Puts the key of each element in it, as its id. | | `Arr::subsets($array, $minLength = 1)` | All the subsets of an array. | | `Arr::toTree($items, $parentField, $childrenField, $parentId = null)` | A flat array with references to the parent into a tree. | | `Arr::treeToList($tree, $nameField, $childrenField)` | A tree into a flat list with levels. | | `Arr::groupToTable($array, $keys = null)` | `['k' => [1, 2]]` into rows. | | `Arr::tableToAssociative($table)` | A table of two columns into an associative array. | | `Arr::toXml($array, $rootElement = 'root')` | An array into XML. | ## Dot notation ```php use Derafu\Support\Arr; Arr::dot(['a' => ['b' => 1, 'c' => [2, 3]]]); // ['a.b' => 1, 'a.c.0' => 2, 'a.c.1' => 3] Arr::nested(['a.b' => 1, 'a.c' => 2, 'd' => 3]); // ['a' => ['b' => 1, 'c' => 2], 'd' => 3] ``` `dot()` takes a `$prefix` that is put before every key (`Arr::dot(['b' => 1], 'a')` is `['a.b' => 1]`). ## Casting `cast()` goes through the array, and in all its levels it trims the texts, turns the numeric texts into `int` or `float`, and replaces the empty texts with `$emptyValue` (`''` by default, which leaves them as they are). ```php Arr::cast(['a' => ' x ', 'b' => '', 'c' => ['d' => '5']], null); // ['a' => 'x', 'b' => null, 'c' => ['d' => 5]] ``` It does not turn `true` or `null` written as texts into values: for that, see [Caster](strings#caster). ## Trees `toTree()` uses the **keys** of the array as the identifiers of the items, and the field `$parentField` of each item has the **key** of its parent. The items of the root are the ones whose parent is `$parentId` (`null` by default). The field of the parent is removed from each item, and the children go in `$childrenField`: ```php $items = [ 1 => ['parent_id' => null, 'name' => 'root'], 2 => ['parent_id' => 1, 'name' => 'a'], 3 => ['parent_id' => 2, 'name' => 'b'], 4 => ['parent_id' => 1, 'name' => 'c'], ]; $tree = Arr::toTree($items, 'parent_id', 'children'); // [1 => ['name' => 'root', 'children' => [ // 2 => ['name' => 'a', 'children' => [3 => ['name' => 'b', 'children' => []]]], // 4 => ['name' => 'c', 'children' => []], // ]]] ``` If the items come from a database as a list, key them by their id first (`array_column($rows, null, 'id')`). An item without the field of the parent is skipped. `treeToList()` goes the other way, in depth order. Each element has its `name` (from `$nameField`) and its `level` (0 for the root), under the same key that it had: ```php Arr::treeToList($tree, 'name', 'children'); // [1 => ['name' => 'root', 'level' => 0], 2 => ['name' => 'a', 'level' => 1], // 3 => ['name' => 'b', 'level' => 2], 4 => ['name' => 'c', 'level' => 1]] ``` ## Tables ```php Arr::groupToTable(['k1' => [1, 2], 'k2' => [3, 4]]); // [['k1' => 1, 'k2' => 3], ['k1' => 2, 'k2' => 4]] Arr::tableToAssociative([['a', 1], ['b', 2]]); // ['a' => 1, 'b' => 2] ``` `tableToAssociative()` needs exactly two columns in each row; a row that does not have them is an `InvalidArgumentException` that says which one. ## Other helpers ```php Arr::subsets([1, 2, 3]); // [[1], [2], [1, 2], [3], [1, 3], [2, 3], [1, 2, 3]] Arr::subsets([1, 2, 3], 2); // [[1, 2], [1, 3], [2, 3], [1, 2, 3]] Arr::ensureIdInElements(['u1' => ['n' => 1], 'u2' => ['n' => 2]], 'id'); // ['u1' => ['id' => 'u1', 'n' => 1], 'u2' => ['id' => 'u2', 'n' => 2]] Arr::toXml(['a' => 1, 'b' => ['c' => 'x&y']], 'r'); // 1x&y ``` `subsets()` gives `2^n` subsets: do not use it with more than a few elements. `ensureArrayAtPath()` changes the array that it is given (it is passed by reference): if the value at the path is a single associative array, it becomes a list with that array as its only element. --- Last updated on 08/10/2026