Merging array values into single key and multiple values in php - php

Question

I want the array to merge into a key value pair. look at the example below
Here is my code and array $aExtraFilter
array (size=4)
0 =>
array (size=2)
'key' => string 'CookTech' (length=8)
'value' => string 'Broil' (length=5)
1 =>
array (size=2)
'key' => string 'CookTech' (length=8)
'value' => string 'Pan Fry' (length=7)
2 =>
array (size=2)
'key' => string 'CookSkills' (length=10)
'value' => string 'Intro' (length=5)
3 =>
array (size=2)
'key' => string 'CookSkills' (length=10)
'value' => string 'Knife Skills' (length=12)
Here is my code:
$aExtraFilter2 = [];
$extrafilterkey = '';
$extrafiltervalue = [];
foreach ($aExtraFilter as $key => $value) {
$extrafilterkey = $value['key'];
$aExtraFilter2[$extrafilterkey] = [];
array_push($extrafiltervalue, $value['value']);
$aExtraFilter2[$extrafilterkey] = implode(',', $extrafiltervalue);
}
var_dump($aExtraFilter2);
the output is :
array (size=2)
'CookTech' => string 'Broil,Pan Fry' (length=13)
'CookSkills' => string 'Broil,Pan Fry,Intro,Knife Skills' (length=32)
I want it to look like this:
array (size=2)
'CookTech' => string 'Broil,Pan Fry' (length=13)
'CookSkills' => string 'Intro,Knife Skills' (length=32)
I think I'm almost there but I guess I need some help.

Answer 1

This line does nothing because it is superseded just a bit later as the same variable is being set:
$aExtraFilter2[$extrafilterkey] = [];
This line appends to the array regardless of what you have as $value['key'], which is why you get all keys lumped together in the output:
array_push($extrafiltervalue, $value['value']);
This will produce a desired output:
// fill array of arrays
$aExtraFilter2 = [];
foreach ($aExtraFilter as $key => $value) {
if (!array_key_exists($value['key'], $aExtraFilter2)) $aExtraFilter2[$value['key']] = [];
$aExtraFilter2[$value['key']][] = $value['value'];
}
// convert to string (if needed at all, depends on what you're doing later)
foreach ($aExtraFilter2 as $key => $set) {
$aExtraFilter2[$key] = join(',', $set);
}

Answer 2

The typical way to code this is by creating a temporary structure, based on the key and comprising an array with the values:
$tmp = [];
foreach ($aExtraFilter as $pair) {
$tmp[$pair['key']][] = $pair['value'];
}
The structure would look like this afterwards:
[
'CookTech' => ['Broil', 'Pan Fry'],
'CookSkills' => ['Intro', 'Knife Skills'],
]
Then, you map that array against the representation you want to have:
$aExtraFilter2 = array_map(function($values) {
return join(',', $values);
}, $tmp);
See also: array_map()