PHP formatting Array to A New Array - php

Question

Hi guys I am a beginner with PHP and want the best way in terms of performance to convert this array:
$old = array(
20 =>
array(
'name' => 'Heels',
'path' => '1/2/10/15/20',
),
15 =>
array(
'name' => 'Sandals',
'path' => '1/2/80/96/15',
),
10 =>
array(
'name' => 'Trainers',
'path' => '1/2/80/96/10',
),
);
To this:
$new = array(
20 =>
array(
'value' => 20,
'label' => 'Trainers > Sandals > Heels',
),
);
There is going to be loads of records surely exploding the paths and mapping them with the ids is going to slow it down in terms of performance just wondering whether there is a more efficient way if possible thanks.

Answer 1

If I understand correctly, you're trying to get the latest path relevant to each category and output it as a breadcrumb.
You can first sort the keys (ids) and then loop through the array creating the breadcrumb.
arsort($paths); # This gives the desired output in OP but makes more sense to use krsort() to sort DESC not ASC
$breadcrumb = (object) array (
'value' => array_keys($paths)[count($paths) - 1], # Get the highest id - if using krsort() use array_keys($paths)[0]
'labels' => implode(' > ', array_column($paths, 'name'));
);
# Update derived from The fourth bird's answer which skips the need for the foreach().
# Concept is to build an array of the labels to then make look pretty with the > effect
Here is a demo.
Output:
object (stdClass) (2) {
["value"] => int(20)
["labels"] => string(26) "Trainers > Sandals > Heels"
}

Answer 2

Another option could be to first create a mapper of the keys and the names. Then you could take the key from the mapper to create the path:
$result = [];
$mapper = array_combine(array_keys($old), array_column($old, 'name'));
foreach ($old as $key => $value) {
$path = implode(' > ', array_map(function($x) use ($mapper) {
return $mapper[(int)$x];
}, explode('/', $value['path'])));
$result[$key] = ['value' => $key,'label' => $path];
}
print_r($result);
Php demo

Answer 3

This is the hardcoded way, but i think you need to give a bit more information to get a dynamic solution.
<?php
$old = array(
20 =>
array(
'name' => 'Heels',
'path' => '1/2/10/15/20',
),
15 =>
array(
'name' => 'Sandals',
'path' => '1/2/80/96/15',
),
10 =>
array(
'name' => 'Trainers',
'path' => '1/2/80/96/10',
),
);
ksort($old);
$breadcrumbs = [];
$currentKey = 0;
foreach ( $old as $itemKey => $item) {
$currentKey = $itemKey;
$breadcrumbs[] = $item;
}
$new = [$currentKey] = [
'value' => $currentKey,
'label' => implode(' > ', $breadcrumbs)
];
printf($new);