Reduce array of associative arrays to associative array

Question

Is there an idiomatic way (some existing function) to reduce

[[0 => 'zero'], [1 => 'one']]

to

[0 => 'zero', 1 => 'one']

?

It is easy to just create a loop that does the job, but it seems inefficient, and I would clearly prefer a one-liner here.

Edit: Oh, and it is just random here that 0 and 1 follow each other. The array could also be [[2 => 'two'], [3 => 'three']]

when downvote, please state in a comment why. I find my question totally valid — IceFire
– IceFire, Commented Sep 12, 2019 at 13:56
@FedericoklezCulloca right, I don't. I just heart about the tendency on SO to just distribute downvotes here and there migh drives the entire network less usable. This is a bad tendency and I try to counteract it, when possible. But for me personally, yeah, whatever — IceFire
– IceFire, Commented Sep 12, 2019 at 14:02

Rakesh Jakhar · Accepted Answer · 2019-09-12 15:48:34Z

6

You can use array_merge with ... splat operator

$a = [[0 => 'zero'], [1 => 'one']];
print_r(array_merge(...$a));

Solution II: Preserve keys

$a = [[1 => 'one'], [0 => 'zero']];
$r = [];
array_walk($a, function($v, $k) use (&$r){ $r += $v;});
print_r($r);

Working demo : https://3v4l.org/9sRaE

edited Sep 12, 2019 at 15:48

answered Sep 12, 2019 at 13:53

Rakesh Jakhar

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6 Comments

u_mulder Over a year ago

Or call_user_func_array when ... is not supported.

René Beneš Over a year ago

Wow, that's what I call a one-liner!

ɴᴀᴛᴇ ᴅᴇᴠ Over a year ago

Note that this ignores the keys in the original array, so if [1 => 'one'] is the first item in the array it becomes 0 => 'one' in the output: 3v4l.org/6UopE

IceFire Over a year ago

@naththedeveloper oh, but this is actually important here

Rakesh Jakhar Over a year ago

@IceFire solution II has the preserve keys

|

Dan Chadwick · Accepted Answer · 2021-01-04 02:58:54Z

0

Assuming that you want keys preserved, and assuming that in the case of conflicting keys, you want the first value, array_reduce is well-suited to the task.

$r = array_reduce($a, function ($acc, $v) { return $acc + $v; }, []);

This is functionally identical to @Rakesh Jakhar's solution. I think it's semantically more faithful to the problem and avoids having the initialize $r and the use clause.

In php 7.4, this could be written a bit nicer with an arrow function:

$r = array_reduce($a, fn($acc, $v) => $acc + $v, []);

https://www.php.net/manual/en/function.array-reduce.php

answered Jan 4, 2021 at 2:58

Dan Chadwick

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