PHP Laravel 5.5 collections flatten and keep the integer keys?

Question

I have the following array :

$array = [
    '2' => ['3' => ['56' => '2'], '6' => ['48' => '2']],
    '4' => ['4' => ['433' => '2', '140' => '2'], '8' => ['421' => '2', '140' => '2']],
    '5' => ['5' => ['88' => '4', '87' => '2']]
];

The following code (flattening) should return it by preserving keys, but it doesnt?

collect($array)->flatten(1);

should give me

[
    '3' => ['56' => '2'],
    '6' => ['48' => '2'],
    '4' => ['433' => '2', '140' => '2'],
    '8' => ['421' => '2', '140' => '2'],
    '5' => ['88' => '4', '87' => '2']
]

However it loses the keys, and just gives array results :/ Am I using it wrong? How should I flatten and preserve keys?

I don't believe `flatten` supports maintaining keys - how would you expect it to work if the keys in a lower level weren't unique? — iainn, Dec 11 '17 at 16:26
OK, thanks. It makes sense in retrospect why flatten wouldn't keep the keys. — GTMeteor, Dec 11 '17 at 18:42

score 52 · Accepted Answer · answered Apr 05 '18 at 06:02

52

An elegant solution is to use the mapWithKeys method. This will flatten your array and keep the keys:

collect($array)->mapWithKeys(function($a) {
    return $a;
});

The mapWithKeys method iterates through the collection and passes each value to the given callback. The callback should return an associative array containing a single key / value pair

answered Apr 05 '18 at 06:02

bmagg

906
8
6

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It can be more elegant/shorter now with arrow function. Works only with PHP 7.4 and above `collect($array)->mapWithKeys(fn($a) => $a);` – Ashraf Kamarudin Sep 10 '20 at 08:24
Very nice, thanks. Since map doesn't flatten, it's unintuitive that map with keys would. – Joel Mellon Oct 31 '21 at 18:11
nice working. thanks – Sanjok Dangol Dec 15 '21 at 03:20
1

same can be achieved with `collect($array)->flatMap(fn ($v) => $v)` which has the added bonus of having the word `flat` for a more expressive statement, although the `fn ($v) => $v` part ruins it. – iSWORD Mar 10 '22 at 08:57

score 2 · Answer 2 · answered Dec 11 '17 at 16:44

2

You can't use flatten() here. I don't have an elegant solution, but I've tested this and it works perfectly for your array:

foreach ($array as $items) {
    foreach ($items as $key => $item) {
        $newArray[$key] = $item;
    }
}

dd($newArray);

answered Dec 11 '17 at 16:44

Alexey Mezenin

158,981
26
290
279

1

This did work. Trying to avoid foreach'es, but it did. thanks. – GTMeteor Dec 11 '17 at 18:42

PHP Laravel 5.5 collections flatten and keep the integer keys?

2 Answers2