====== PHP RFC: Add array_group function ======
  * Version: 2.0
  * Date: 2021-11-28
  * Author: Hassan Ahmed, 7snovic@gmail.com
  * Status: Declined
  * First Published at: https://wiki.php.net/rfc/array_column_results_grouping

===== Introduction =====
This RFC is to implement a new function to PHP that upgrades the functionality of array_column to group similar results that share the same index_key into a multidimensional array. the current behavior of array_column is to return a single result and ignore the rest of the results that share the same index.

===== Proposal =====
This RFC is to add a new function called array_group
<code php>array_group(array $array, int|string|null $column_key, int|string|null $index_key = null)</code>

The current behavior is when you have multiple elements share the same key, it will be overwritten.
let's assume that we have the following.

<code php>
<?php

$array = [
    ['id' => 1, 'name' => 'hassan'],
    ['id' => 2, 'name' => 'sara'],
    ['id' => 3, 'name' => 'selim'],
    ['id' => 4, 'name' => 'chris'],
    ['id' => 5, 'name' => 'sara'],
];
</code>

when we use array_column with this the output will be

<code php>
print_r(array_column($array, null, 'name'));
Array
(
    [hassan] => Array
        (
            [id] => 1
            [name] => hassan
        )

    [sara] => Array
        (
            [id] => 5
            [name] => sara
        )

    [selim] => Array
        (
            [id] => 3
            [name] => selim
        )

    [chris] => Array
        (
            [id] => 4
            [name] => chris
        )

)
</code>

The RFC implements a new function called array_group to group the results in an indexed array to group all the similar elements, so we can use :

<code php>
print_r(array_group($array, null, 'name'));
Array
(
    [hassan] => Array
        (
            [0] => Array
                (
                    [id] => 1
                    [name] => hassan
                )

        )

    [sara] => Array
        (
            [0] => Array
                (
                    [id] => 2
                    [name] => sara
                )

            [1] => Array
                (
                    [id] => 5
                    [name] => sara
                )

        )

    [selim] => Array
        (
            [0] => Array
                (
                    [id] => 3
                    [name] => selim
                )

        )

    [chris] => Array
        (
            [0] => Array
                (
                    [id] => 4
                    [name] => chris
                )

        )

)
</code>

===== Backward Incompatible Changes =====
No backward incompatible breaks.

===== Proposed PHP Version(s) =====
Next PHP 8.x, currently PHP 8.2.

===== RFC Impact =====
==== To Existing Extensions ====
Standard ext

===== Proposed Voting Choices =====
Yes/No vote.

===== Voting =====

Started at : 2021-12-21
Ends at : 2022-01-04

<doodle title="Add array_group function to PHP" auth="hassan" voteType="single" closed="true">
   * Yes
   * No
</doodle>

===== Implementation =====
[[https://github.com/php/php-src/pull/7698|Implementing array_group function]]