PHP wrap array elements in separate arrays - php

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" ],
]

Answer 1

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);

Answer 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
)
)

Answer 3

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);

Answer 4

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