Associative Array, find duplicates in values

Question

The array that I use is an array merged from three different arrays (3 different mysql results). Each array is an associative array with a few fields and the count field is the field I need.

The following piece of array is a double entry. I want to check the array and check if there are duplicates ( id field) and calculate the sum of the count field. What would be the best-practice to solve this issue?

array(21) {
[2] => array(6) {
  ["id"] => string(2) "71"
  ["artist"] => string(7) "Arsenal"
  ["title"] => string(10) "Oyebo Soul"
  ["genres_id"] => string(2) "13"
  ["mbid"] => string(36) "0048d294-1557-4e05-8c82-8bc3f8f11923"
  ["count"] => string(1) "4"
}
[3] => array(6) {
  ["count"] => string(1) "3"
  ["id"] => string(2) "71"
  ["artist"] => string(7) "Arsenal"
  ["title"] => string(10) "Oyebo Soul"
  ["genres_id"] => string(2) "13"
  ["mbid"] => string(36) "0048d294-1557-4e05-8c82-8bc3f8f11923"
}

The result would be this:

[3] => array(6) {
  ["count"] => string(1) "7"
  ["id"] => string(2) "71"
  ["artist"] => string(7) "Arsenal"
  ["title"] => string(10) "Oyebo Soul"
  ["genres_id"] => string(2) "13"
  ["mbid"] => string(36) "0048d294-1557-4e05-8c82-8bc3f8f11923"
}

Hope this makes any sense. Thanks in advance

Answer 1

There's bound to be a ton of different ways to approach this problem, but the first one that popped into my head was to make use of array_reduce() on each set of "duplicate" albums:

// Group and index the albums by 'mbid'...
$indexed = array();

foreach ($albums as $album) {
    $indexed[$album['mbid']][] = $album;
}

// Reduce all the album groups by simply totaling their 'count's...
$indexed = array_map(function($albums) {
    return array_reduce($albums, function($a, $b) {
        $a['count'] += $b['count'];
        return $a;
    });
}, $indexed);

Note: This solution assumes that all the information in each album duplicate is identical except the count , as is the case in your example.