Regroup multidimensional array to reverse presentation of many-to-many relationship - php

Question

I need to perform iterated explosions on values in one column of my two dimensional array, then re-group the data to flip the relational presentation from "tag name -> video id" to "video id -> tag name".
Here is my input array:
$allTags = [
[
"name" => "TAG-ONE",
"video" => "64070,64076,64110,64111",
],
[
"name" => "TAG-TWO",
"video" => "64070,64076,64110,64111",
],
[
"name" => "TAG-THREE",
"video" => "64111",
]
];
I want to isolate unique video ids and consolidate all tag names (as comma-separayed values) that relate to each video id.
Expected output:
$allTagsResult = [
[
"name" => "TAG-ONE,TAG-TWO",
"video" => "64070",
],
[
"name" => "TAG-ONE,TAG-TWO",
"video" => "64076",
],
[
"name" => "TAG-ONE,TAG-TWO",
"video" => "64110",
],
[
"name" => "TAG-ONE,TAG-TWO,TAG-THREE",
"video" => "64111",
],
];
Somehow I did it by checking the value using nested loops but I wish to know if you guys can suggest any shortest method to get the expected output.

Answer 1

If you want to completely remove foreach() loops, then using array_map(), array_walk_recursive(), array_fill_keys() etc. can do the job. Although I think that a more straightforward answer using foreach() would probably be faster, but anyway...
$out1 = array_map(function ($data) {
return array_fill_keys(explode(",", $data['video']), $data['name']); },
$allTags);
$out2 = [];
array_walk_recursive( $out1, function ( $data, $key ) use (&$out2) {
if ( isset($out2[$key])) {
$out2[$key]['name'] .= ",".$data;
}
else {
$out2[$key] = [ 'name' => $data, 'video' => $key ];
}
} );
print_r($out2);
will give...
Array
(
[64070] => Array
(
[name] => TAG-ONE,TAG-TWO
[video] => 64070
)
[64076] => Array
(
[name] => TAG-ONE,TAG-TWO
[video] => 64076
)
[64110] => Array
(
[name] => TAG-ONE,TAG-TWO
[video] => 64110
)
[64111] => Array
(
[name] => TAG-ONE,TAG-TWO,TAG-THREE
[video] => 64111
)
)
if you want to remove the keys, then
print_r(array_values($out2));
The code could be compressed by piling all of the code onto single lines, but readability is more useful sometimes.

Answer 2

Another method if you don't like looping:
$video_ids = array_flip(array_unique(explode(",",implode(",",array_column($allTags,'video')))));
$result = array_map(function($id){
return ['name' => '','video' => $id];
},array_flip($video_ids));
array_walk($allTags,function($tag_data) use (&$result,&$video_ids){
$ids = explode(",",$tag_data['video']);
foreach($ids as $id) $result[$video_ids[$id]]['name'] = empty($result[$video_ids[$id]]['name']) ? $tag_data['name'] : $result[$video_ids[$id]]['name'] . "," . $tag_data['name'];
});
Demo: https://3v4l.org/vlIks

Answer 3

Below is one way of doing it.
$allTags = [
'0' => [
"name" => "TAG-ONE",
"video" => "64070,64076,64110,64111",
],
'1' => [
"name" => "TAG-TWO",
"video" => "64070,64076,64110,64111",
],
'2' => [
"name" => "TAG-THREE",
"video" => "64111",
]
];
$allTagsResult = array();
$format = array();
foreach( $allTags as $a ) {
$name = $a['name'];
$videos = explode(',', $a['video']);
foreach( $videos as $v ) {
if( !isset( $format[$v]) ) {
$format[$v] = array();
}
$format[$v][] = $name;
}
}
foreach( $format as $video => $names) {
$allTagsResult[] = array('name' => implode(',', $names), 'video' => $video);
}
echo '<pre>';
print_r($allTagsResult);
die;
You can check Demo

Answer 4

I am typically in favor of functional style coding, but for this task I feel it only serves to make the script harder to read and maintain.
Use nested loops and explode the video strings, then group by those video ids and concatenate name strings within each group. When finished iterating, re-index the array.
Code: (Demo)
$result = [];
foreach ($allTags as $tags) {
foreach (explode(',', $tags['video']) as $id) {
if (!isset($result[$id])) {
$result[$id] = ['video' => $id, 'name' => $tags['name']];
} else {
$result[$id]['name'] .= ",{$tags['name']}";
}
}
}
var_export(array_values($result));
Output:
array (
0 =>
array (
'video' => '64070',
'name' => 'TAG-ONE,TAG-TWO',
),
1 =>
array (
'video' => '64076',
'name' => 'TAG-ONE,TAG-TWO',
),
2 =>
array (
'video' => '64110',
'name' => 'TAG-ONE,TAG-TWO',
),
3 =>
array (
'video' => '64111',
'name' => 'TAG-ONE,TAG-TWO,TAG-THREE',
),
)