php strangely nested key/value array - how to transform/map to be more usable?

Question

The Microsoft QnAMaker API is returning a JSON key/value array (Metadata) in the following format:

$array = [[
    "name" => "someName1",
    "value" => "someValue1",
],
[
    "name" => "someName2",
    "value" => "someValue2",
],
 ..etc..
];

How do i transform it to be in the following more usable format:

$array = [
    "someName1" => "someValue1",
    "someName2" => "someValue2",
    ..etc..
];

I know I can do it using a loop... Is there a way to leverage on built in functions?

If a loop is the only way, how would you write it and why (performance/readibility/etc.)?

Could you not simply store `$array[0][0]` in a temp variable and then remove the second index --> `$array[0][0]` -- then set `$array[0]` ? — Zak, Oct 23 '18 at 17:47
Any reason you don't want to just use a loop? It's only like 3 lines — GrumpyCrouton, Oct 23 '18 at 17:56
@Leo after looking at it more closely, what you are asking is a little more complicated as far as restructuring your array -- You are trying to use key **values** as key **identifiers** -- This is going to require a loop .. There's just no other way around it. — Zak, Oct 23 '18 at 17:56
@GrumpyCrouton - loop is ok... i just wondered if there was something i could leverage on... I was hoping for someone more fluent in PHP to show me a double filter and combine solution or thereabout... — Leo, Oct 23 '18 at 17:57
Sounds like what you're thinking of is flatmap. PHP doesn't have that built-in. Other folks have created their own: https://gist.github.com/davidrjonas/8f820ab0c75534b45189eba1d1fbeb23 ... which is effectively what has been posted already. — Brian Wagner, Oct 23 '18 at 18:08

GrumpyCrouton · Answer 1 · 2018-10-23T17:59:18.527

2

There isn't really a way besides a loop, so just loop through the array, and create a new array the way you need it.

$new_array = [];
foreach($array as $row) {
    $new_array[$row['name']] = $row['value'];
}

print_r($new_array);

There may be a few functions you can tie together to do what you want, but in general, the loop would probably be more readable and easier in overall.

edited Oct 23 '18 at 17:59

answered Oct 23 '18 at 17:44

GrumpyCrouton

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2

It's a much simpler way of doing it and more maintainable IMHO. – Nigel Ren Oct 23 '18 at 18:02

Nigel Ren · Answer 2 · 2018-10-23T17:59:14.690

2

This uses a combination of array_map() to re-map each element and then array_merge() to flatten the results...

print_r(array_merge(...array_map(function($data) 
                         { return [ $data['name'] => $data['value']]; }
                       , $array)));

It's not very elegant and would be interesting to see other ideas around this.

Which gives...

Array
(
    [someName1] => someValue1
    [someName2] => someValue2
)

edited Oct 23 '18 at 17:59

answered Oct 23 '18 at 17:50

Nigel Ren

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This would produce `Array ( [someName1] => someName2 [someValue1] => someValue2 )` – Zak Oct 23 '18 at 17:51
1

@Zak, thanks - I've altered the code and actually checked the results this time. – Nigel Ren Oct 23 '18 at 17:59
`...array_map` - sorry i'm new to php... what does `...` in front of function do? – Leo Oct 23 '18 at 18:03
The ... (also called the splat operator) passes each element from an array as a parameter. – Nigel Ren Oct 23 '18 at 18:04
@LeonardoSeccia It unpacks all the variables returned from array_map as a separate parameter – GrumpyCrouton Oct 23 '18 at 18:04
1

@Leo -- It's called a "splat" operator https://lornajane.net/posts/2014/php-5-6-and-the-splat-operator – Zak Oct 23 '18 at 18:04
This is genius... But it looks like i am better of with a loop. Thank you though. – Leo Oct 23 '18 at 18:08
1

Anyone else maintaining your code will thank you for going with a loop :) – Nigel Ren Oct 23 '18 at 18:08

Progrock · Answer 3 · 2018-10-23T18:16:18.263

2

As my previous answer was a dupe of GrumpyCroutons, I thought I'd rewrite with many array functions for good measure. (But don't use this, just do a simple foreach).

<?php
array_walk($array, function($v) use (&$result) {
    $result[array_shift($v)] = array_values($v)[0];
});

var_export($result);

Output:

array (
  'someName1' => 'someValue1',
  'someName2' => 'someValue2',
)

edited Oct 23 '18 at 18:16

answered Oct 23 '18 at 18:04

Progrock

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@GrumpyCrouton et al, hold your horses, I hadn't seen any answers when posting. – Progrock Oct 23 '18 at 18:06
1

This is a good and valid answer - but I would note that [`array_walk()` may not necessarily be faster than `foreach()`](http://www.ktorides.com/2015/02/php-array_walk-vs-foreach/) (Also, since this is a good and valid answer, I gave you an upvote to balance out that downvote you got when your answer was a duplicate) – GrumpyCrouton Oct 23 '18 at 18:26
1

@GrumpyCrouton I would say valid, but not good, rather ugly. I do note that a simple foreach would be preferable and dare I say, the _pythonic_ way to do this. – Progrock Oct 24 '18 at 03:42

Progrock · Accepted Answer · 2018-10-24T07:14:15.470

2

If it looks JSONish, array_column helps. Simply:

<?php
var_export(array_column($array, 'value', 'name'));

Output:

array (
    'someName1' => 'someValue1',
    'someName2' => 'someValue2',
)

edited Oct 24 '18 at 07:14

answered Oct 24 '18 at 07:08

Progrock

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Nice solution, I didn't know you could pass 3 variables to `array_column()` like that. – GrumpyCrouton Oct 24 '18 at 14:11
1

@GrumpyCrouton I did, and yet it took more than a while to come back to me. You can get a long way with some simple constructs such as a foreach. I'm always going back to the manual for array function lookups (blushes).. – Progrock Oct 24 '18 at 15:44

pierDipi · Answer 5 · 2018-10-23T18:41:16.010

1

This works:

$res = [];
array_walk($array, function(&$e) use(&$res) {
    $res[$e['name']] = $e['value'];
    unset($e); // this line adds side effects and it could be deleted
});
var_dump($res);

Output:

array(2) { 
   ["someName1"]=> string(10) "someValue1" 
   ["someName2"]=> string(10) "someValue2" 
}

edited Oct 23 '18 at 18:41

answered Oct 23 '18 at 18:18

pierDipi

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Progrock · Answer 6 · 2018-10-24T03:32:02.170

1

You can simply use array_reduce:

<?php
$output = array_reduce($array, function($a, $b) {
    $a[$b['name']] = $b['value'];

    return $a;
});

var_export($output);

Output:

array (
    'someName1' => 'someValue1',
    'someName2' => 'someValue2',
)

edited Oct 24 '18 at 03:32

answered Oct 24 '18 at 03:24

Progrock

7,373
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Progrock · Answer 7 · 2018-10-24T03:50:01.127

While getting a shift on (a non-foreach):

<?php
$c = $array;
while($d = array_shift($c))
    $e[array_shift($d)] = array_shift($d);

var_export($e);

Output:

array (
    'someName1' => 'someValue1',
    'someName2' => 'someValue2',
)

Although it suggests in the comments in the manual that shifting is more expensive than popping. You could replace the initial assignment to $c above with an array_reverse and the while-shift with a while-pop.

However, either approach is probably lousy compared to a foreach, but here for who knows whos amusement.

php strangely nested key/value array - how to transform/map to be more usable?

7 Answers7