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References: <289E585B-EF8B-4B17-89BE-BE8295FD9FE1@gmail.com>
In-Reply-To: <289E585B-EF8B-4B17-89BE-BE8295FD9FE1@gmail.com>
Date: Tue, 30 May 2023 16:57:22 +0200
Message-ID: <CAB-BujYyz4vFAmi+OKi0rjqViE02eUjDpkkYyAMRCf10t8mNXA@mail.gmail.com>
To: Boro Sitnikovski <buritomath@gmail.com>
Cc: internals@lists.php.net
Content-Type: text/plain; charset="UTF-8"
Subject: Re: [PHP-DEV] [RFC] [Discussion] Add new function `array_group`
From: andreas@dqxtech.net (Andreas Hennings)

Hello Boro,
I think you should include the "expected result" in your code examples.
Maybe this is in your patch file, but I don't think we want to look at
that for discussion.

Cheers
Andreas

On Tue, 30 May 2023 at 13:35, Boro Sitnikovski <buritomath@gmail.com> wrote:
>
> Hello all,
>
> As per the How To Create an RFC instructions, I am sending this e-mail in order to get your feedback on my proposal.
>
> I propose introducing a function to PHP core named `array_group`. This function takes an array and a function and returns an array that contains arrays - groups of consecutive elements. This is very similar to Haskell's `groupBy` function.
>
> For some background as to why - usually, when people want to do grouping in PHP, they use hash maps, so something like:
>
> ```
> <?php
> $array = [
> [ 'id' => 1, 'value' => 'foo' ],
> [ 'id' => 1, 'value' => 'bar' ],
> [ 'id' => 2, 'value' => 'baz' ],
> ];
>
> $groups = [];
> foreach ( $array as $element ) {
>     $groups[ $element['id'] ][] = $element;
> }
>
> var_dump( $groups );
> ```
>
> This can now be achieved as follows (not preserving keys):
>
> ```
> <?php
> $array = [
> [ 'id' => 1, 'value' => 'foo' ],
> [ 'id' => 1, 'value' => 'bar' ],
> [ 'id' => 2, 'value' => 'baz' ],
> ];
>
> $groups = array_group( $array, function( $a, $b ) {
> return $a['id'] == $b['id'];
> } );
> ```
>
> The disadvantage of the first approach is that we are only limited to using equality check, and we cannot group by, say, `<` or other functions.
> Similarly, the advantage of the first approach is that the keys are preserved, and elements needn't be consecutive.
>
> In any case, I think a utility function such as `array_group` will be widely useful.
>
> Please find attached a patch with a proposed implementation. Curious about your feedback.
>
> Best,
>
> Boro Sitnikovski
>