Merge associative arrays with shared column values

Question

I want to merge two arrays based on common column values. Here are my 2 arrays:

$array1 = [
    [
        "total_process_per_category" => "6",
        "category_id" => "1"
    ],
    [
        "total_process_per_category" => "2",
        "category_id" => "2"
    ]
];

$array2 = [
    [
        "total_pinned_per_category" => "16",
        "category_id" => "1"
    ],
    [
        "total_pinned_per_category" => "4",
        "category_id" => "2"
    ]
];

I want to merge these arrays to get:

array (
  0 => 
  array (
    'total_process_per_category' => '6',
    'total_pinned_per_category' => '16',
    'category_id' => '1',
  ),
  1 => 
  array (
    'total_process_per_category' => '2',
    'total_pinned_per_category' => '4',
    'category_id' => '2',
  ),
)

As you can see, both arrays have the same key ['category_id'] and the same value.

I want to get a result where ['total_process_per_category'] and ['total_pinned_per_category'] are placed together on the same array based on their ['category_id'] values.

I got this using nested foreach but it looks ugly. Please tell me a better way.

Answer 1

This can be done without "ugly nested foreach". Merge the two arrays before iterating, grouping by category_id value. After the loop ends, use array_values() to clear the temporary first-level keys.

Code: (Demo) (array_reduce() version)

$result = [];
foreach (array_merge($array1, $array2) as $row) {
    $result[$row['category_id']] = ($result[$row['category_id']] ?? []) + $row;
}
var_export(array_values($result));

Output:

array (
  0 => 
  array (
    'total_process_per_category' => '6',
    'category_id' => '1',
    'total_pinned_per_category' => '16',
  ),
  1 => 
  array (
    'total_process_per_category' => '2',
    'category_id' => '2',
    'total_pinned_per_category' => '4',
  ),
)

Answer 2

You can tryarray_reduce:

$someVariable = 'someValue';
$result = array_reduce(array_merge($array1, $array2), function ($carry, $item) use ($someVariable) {
    if (isset($carry[$item['category_id']])) {
        $carry[$item['category_id']] = array_merge($carry[$item['category_id']], $item);
    } else {
        $carry[$item['category_id']] = $item;
    }
    return $carry;
}, array());

var_dump($result);