Group array by subarray values

In PHP, you can group an array of arrays (subarrays) by the value of a specific key in each subarray using the array_reduce() function. Here is an example:

<?php

$data = [['id' => 1, 'name' => 'Alice', 'group' => 'A'], ['id' => 2, 'name' => 'Bob', 'group' => 'B'], ['id' => 3, 'name' => 'Charlie', 'group' => 'A'], ['id' => 4, 'name' => 'Dave', 'group' => 'B']];

$grouped = array_reduce(
  $data,
  function ($carry, $item) {
    $carry[$item['group']][] = $item;
    return $carry;
  },
  []
);

print_r($grouped);

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This will group the subarrays by the value of the 'group' key, resulting in the following output:

Array
(
    [A] => Array
        (
            [0] => Array
                (
                    [id] => 1
                    [name] => Alice
                    [group] => A
                )

            [1] => Array
                (
                    [id] => 3
                    [name] => Charlie
                    [group] => A
                )

        )

    [B] => Array
        (
            [0] => Array
                (
                    [id] => 2
                    [name] => Bob
                    [group] => B
                )

            [1] => Array
                (
                    [id] => 4
                    [name] => Dave
                    [group] => B
                )

        )

)

You can group by any key which exist in subarray as per requirement.