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Reply-To: Levi Morrison <levi.morrison@datadoghq.com>
Date: Wed, 31 May 2023 17:13:58 -0600
Message-ID: <CAAKU0u=r_V4h1xw=nTGUmHzEErS+UMHOx100LKLf40jz_MEV1A@mail.gmail.com>
To: Boro Sitnikovski <buritomath@gmail.com>
Cc: internals@lists.php.net
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Subject: Re: [PHP-DEV] [RFC] [Discussion] Add new function `array_group`
From: internals@lists.php.net ("Levi Morrison via internals")

On Tue, May 30, 2023 at 5:35=E2=80=AFAM 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 fu=
nction takes an array and a function and returns an array that contains arr=
ays - groups of consecutive elements. This is very similar to Haskell's `gr=
oupBy` 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 =3D [
> [ 'id' =3D> 1, 'value' =3D> 'foo' ],
> [ 'id' =3D> 1, 'value' =3D> 'bar' ],
> [ 'id' =3D> 2, 'value' =3D> 'baz' ],
> ];
>
> $groups =3D [];
> foreach ( $array as $element ) {
>     $groups[ $element['id'] ][] =3D $element;
> }
>
> var_dump( $groups );
> ```
>
> This can now be achieved as follows (not preserving keys):
>
> ```
> <?php
> $array =3D [
> [ 'id' =3D> 1, 'value' =3D> 'foo' ],
> [ 'id' =3D> 1, 'value' =3D> 'bar' ],
> [ 'id' =3D> 2, 'value' =3D> 'baz' ],
> ];
>
> $groups =3D array_group( $array, function( $a, $b ) {
> return $a['id'] =3D=3D $b['id'];
> } );
> ```
>
> The disadvantage of the first approach is that we are only limited to usi=
ng equality check, and we cannot group by, say, `<` or other functions.
> Similarly, the advantage of the first approach is that the keys are prese=
rved, and elements needn't be consecutive.
>
> In any case, I think a utility function such as `array_group` will be wid=
ely useful.
>
> Please find attached a patch with a proposed implementation. Curious abou=
t your feedback.
>
> Best,
>
> Boro Sitnikovski
>

I'm sorry if one of the many replies already mentioned this, but there
was a failed RFC for `array_group`:
https://wiki.php.net/rfc/array_column_results_grouping. Note that I
voted against it for technical reasons (the signature was just awful,
we can do better), but I am not against the idea of adding such helper
functions in principle.