PHP wrap array elements in separate arrays

Question

I have the following array:

$arr = [
    "elem-1" => [ "title" => "1", "desc" = > "" ],
    "elem-2" => [ "title" => "2", "desc" = > "" ],
    "elem-3" => [ "title" => "3", "desc" = > "" ],
    "elem-4" => [ "title" => "4", "desc" = > "" ],
]

First I need to change the value from [ "title" => "1", "desc" = > "" ] to 1 (title's value).

I did this using array_walk:

array_walk($arr, function(&$value, $key) {
    $value = $value["title"];
});

This will replace my value correctly. Our current array now is:

$arr = [
    "elem-1" => "1",
    "elem-2" => "2",
    "elem-3" => "3",
    "elem-4" => "4",
]

Now, I need to transform each element of this array into its own subarray. I have no idea on how to do this without a for loop. This is the desired result:

$arr = [
    [ "elem-1" => "1" ],
    [ "elem-2" => "2" ],
    [ "elem-3" => "3" ],
    [ "elem-4" => "4" ],
]

You could create a new array and do foreach($arr as $value) { $newarray[] = array($value)} but I'm sure there's a built in function that could do that. I just don't know of it — Chad K
– Chad K, Commented Aug 8, 2018 at 20:46
A for loop is straightforward. Since I'm already using array_* functions, I figured it would be nice to have a solution like that. — Maurício Giordano
– Maurício Giordano, Commented Aug 8, 2018 at 20:53

Don't Panic · Accepted Answer · 2018-08-08 20:49:51Z

5

You can change your array_walk callback to produce that array.

array_walk($arr, function(&$value, $key) {
    $value = [$key => $value["title"]];
});

Run the transformed array through array_values if you need to get rid of the string keys.

$arr = array_values($arr);

answered Aug 8, 2018 at 20:49

Don't Panic

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Comments

TommyBs · Accepted Answer · 2018-08-08 20:59:37Z

2

To offer an alternative solution you could achieve all of this with array_map

 <?php

$arr = [
    "elem-1" => [ "title" => "1", "desc" => "" ],
    "elem-2" => [ "title" => "2", "desc" => "" ],
    "elem-3" => [ "title" => "3", "desc" => "" ],
    "elem-4" => [ "title" => "4", "desc" => "" ],
];



function convertToArray($key,$elem){
   return [$key => $elem['title']];
}

$arr = array_map("convertToArray", array_keys($arr), $arr);
echo '<pre>';
print_r($arr);
echo '</pre>';
?>

outputs

  Array
(
    [0] => Array
        (
            [elem-1] => 1
        )

    [1] => Array
        (
            [elem-2] => 2
        )

    [2] => Array
        (
            [elem-3] => 3
        )

    [3] => Array
        (
            [elem-4] => 4
        )

)

answered Aug 8, 2018 at 20:59

TommyBs

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2 Comments

Don't Panic Over a year ago

I was wondering why you deleted it. I was going to suggest the same thing as an alternative.

TommyBs Over a year ago

I realised my first iteration had the wrong output so originally I was just going to delete the whole thing bearing in mind you'd already provided a selected answer. But it was a simple enough fix so I reinstated it just so others could see alternative methods afterall thats how we all learn right?

mickmackusa · Accepted Answer · 2024-10-23 22:41:41Z

0

It doesn't make much sense to use array_walk() and modify by reference because the final result needs to have completely new keys on both levels. In other words, the output structure is completely different from the input and there are no salvageable/mutable parts. Mopping up the modified array with array_values() only adds to the time complexity cost.

array_map() has to bear a cost to time complexity too because array_keys() must be passed in as an additional parameter.

If you want to use array_walk(), use use() to modify the result array. This will allow you to enjoy the lowest possible time complexity.

More concise than array_walk() and cleaner to read, I would probably use a classic foreach() in my own project.

Codes: (Demo)

$result = [];
array_walk(
    $arr,
    function($row, $key) use(&$result) {
        $result[] = [$key => $row['title']];
    }
);

Or:

$result = [];
foreach ($arr as $key => $row) {
    $result[] = [$key => $row['title']];
}
var_export($result);

Or:

var_export(array_chunk(array_map(fn($row) => $row['title'], $arr), 1, true));

edited Oct 23, 2024 at 22:41

answered Jun 14, 2022 at 10:34

mickmackusa♦

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1 Comment

mickmackusa Over a year ago

Related: Convert a flat, associative array into an indexed array of individual associative rows

Ajay Kumar · Accepted Answer · 2018-08-08 21:12:22Z

-2

You need to use array_map like

$new_arr= array_map(function($key,$val){
return [$key => $val['title']];},array_keys($arr),$arr);

edited Aug 8, 2018 at 21:12

answered Aug 8, 2018 at 21:00

Ajay Kumar

976 bronze badges

2 Comments

Don't Panic Over a year ago

array_map doesn't get the keys by default. You need to pass them in as another array. Check out the other answer from TommyBs

Ajay Kumar Over a year ago

Yes sure.. I forgot to add that bcoz I am typing on mobile sorry

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