Laravel Arr::flatten(): Flatten Nested Arrays

Arr::flatten() collapses a multi-dimensional PHP array into a single flat array. Laravel ships it as part of the Illuminate\Support\Arr class. It works at any nesting depth and takes an optional $depth parameter to control how many levels it digs. The result is always a re-indexed, one-dimensional array of values.

:::note[TL;DR]

Arr::flatten($array) flattens to a single level by default (depth = INF)
Pass a second argument $depth to limit how many levels are collapsed
Array keys are discarded — only values are kept
To preserve keys, use Arr::dot() instead
Requires use Illuminate\Support\Arr; at the top of your file :::

How do you use Arr::flatten() in Laravel?

Import the class first, then call the static method:

use Illuminate\Support\Arr;

$data = [
    'country' => 'India 🇮🇳',
    'languages' => [
        'Gujarati',
        'Hindi',
        'Sanskrit',
        'Tamil',
        'Urdu',
    ],
];

$flat = Arr::flatten($data);

Laravel extracts all values and returns them as a re-indexed array. The country key and languages key are gone — only their values remain:

array:6 [
  0 => "India 🇮🇳"
  1 => "Gujarati"
  2 => "Hindi"
  3 => "Sanskrit"
  4 => "Tamil"
  5 => "Urdu"
]

The scenario: You’re pulling a list of available shipping zones from a config file. The config is nested by region and country. You need a flat list of zone names to pass to a <select> dropdown. Arr::flatten() gets you there in one call instead of a nested loop.

:::warning Arr::flatten() discards all array keys. The output is always a numerically re-indexed array of values. If you need to preserve key-value pairs from a nested structure, use Arr::dot() instead — it converts nesting into dot-notation keys like languages.0, languages.1. :::

How does the depth parameter control flattening?

Without a depth argument, Arr::flatten() recurses all the way down. You can limit it. The $depth parameter specifies how many levels to unwrap.

This array has three levels of nesting. Flattening to depth 2 stops before the innermost [6, 7]:

use Illuminate\Support\Arr;

$data = [[12, [2, 4], 124, 7, 10, 8, [15, [6, 7]]]];

$partialFlat = Arr::flatten($data, 2);

At depth 2, the outer two levels collapse but the deepest [6, 7] pair stays intact:

array:9 [
  0 => 12
  1 => 2
  2 => 4
  3 => 124
  4 => 7
  5 => 10
  6 => 8
  7 => 15
  8 => array:2 [
    0 => 6
    1 => 7
  ]
]

Passing INF (or omitting the argument entirely) flattens everything, including that last pair:

$fullyFlat = Arr::flatten($data, INF);

array:10 [
  0 => 12
  1 => 2
  2 => 4
  3 => 124
  4 => 7
  5 => 10
  6 => 8
  7 => 15
  8 => 6
  9 => 7
]

How does Arr::flatten() compare to plain PHP alternatives?

PHP doesn’t have a built-in function for arbitrary-depth flattening. The closest native option is array_merge(...$array) with the splat operator — but it only works one level deep:

// Plain PHP: works only for one level of nesting
$nested = [[1, 2], [3, 4], [5, 6]];
$flat   = array_merge(...$nested);

// Result: [1, 2, 3, 4, 5, 6] — correct for this case

As soon as you have deeper nesting, array_merge(...$nested) either errors or only partially flattens:

$deep = [[1, [2, 3]], [4, [5, 6]]];
$flat = array_merge(...$deep);

// Result: [1, [2, 3], 4, [5, 6]] — inner arrays survive

Arr::flatten($deep) handles this correctly, digging all the way through. Use array_merge(...$nested) when you know your data is only one level deep and you want to avoid the dependency. Use Arr::flatten() for anything that might nest further.

See Flatten array to get IDs from an Eloquent collection if what you actually need is a flat list of IDs from a query result — there’s a more direct method for that case.

What’s the difference between Arr::flatten() and Arr::dot()?

Arr::flatten() drops keys and gives you a plain list of values. Arr::dot() keeps keys by converting nested keys into dot-notation strings:

use Illuminate\Support\Arr;

$data = [
    'user' => [
        'name' => 'Alice',
        'role' => 'admin',
    ],
];

// Arr::flatten — values only
Arr::flatten($data);
// ['Alice', 'admin']

// Arr::dot — key-value pairs preserved
Arr::dot($data);
// ['user.name' => 'Alice', 'user.role' => 'admin']

If you need to access nested config values, validate deep arrays, or build flat cache keys from structured data, Arr::dot() is the right tool. If you just need a list of values, Arr::flatten() is simpler.

Summary

Arr::flatten($array) collapses all nesting by default. Pass $depth to stop at a specific level.
Keys are always discarded. The result is a sequential integer-keyed array.
For key-preserving flattening, use Arr::dot().
Native array_merge(...$nested) works for single-level nesting only. Arr::flatten() handles arbitrary depth.
Requires importing Illuminate\Support\Arr. Works in Laravel 8 through 12.

FAQ

Does Arr::flatten() modify the original array? No. It returns a new array and leaves the input unchanged.

What happens if I pass an already-flat array? It returns a copy with re-indexed keys. No error, no change in values.

Does it work on Eloquent collection results? Not directly — Eloquent returns a Collection object, not a plain array. Call ->toArray() on the collection first, then pass the result to Arr::flatten().

Can I flatten an empty array? Yes. Arr::flatten([]) returns [] without errors.

Where is Arr::flatten() documented? In the Laravel 12 Helpers documentation under the Array Helpers section.

Laravel Arr::flatten(): Flatten Nested Arrays

How do you use Arr::flatten() in Laravel?

How does the depth parameter control flattening?

How does Arr::flatten() compare to plain PHP alternatives?

What’s the difference between Arr::flatten() and Arr::dot()?

Summary

FAQ

What to Read Next

System_Continuity

Get the Last Element of an Array in PHP and Laravel

Create a Laravel Collection from an Array

Remove Elements from a Laravel Collection