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Date: Thu, 1 Jun 2023 01:19:19 +0200
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References: <289E585B-EF8B-4B17-89BE-BE8295FD9FE1@gmail.com>
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To: Levi Morrison <levi.morrison@datadoghq.com>
Subject: Re: [PHP-DEV] [RFC] [Discussion] Add new function `array_group`
From: buritomath@gmail.com (Boro Sitnikovski)



> On 1.6.2023, at 01:13, Levi Morrison <levi.morrison@datadoghq.com> =
wrote:
>=20
> On Tue, May 30, 2023 at 5:35=E2=80=AFAM Boro Sitnikovski =
<buritomath@gmail.com> wrote:
>>=20
>> Hello all,
>>=20
>> As per the How To Create an RFC instructions, I am sending this =
e-mail in order to get your feedback on my proposal.
>>=20
>> 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.
>>=20
>> For some background as to why - usually, when people want to do =
grouping in PHP, they use hash maps, so something like:
>>=20
>> ```
>> <?php
>> $array =3D [
>> [ 'id' =3D> 1, 'value' =3D> 'foo' ],
>> [ 'id' =3D> 1, 'value' =3D> 'bar' ],
>> [ 'id' =3D> 2, 'value' =3D> 'baz' ],
>> ];
>>=20
>> $groups =3D [];
>> foreach ( $array as $element ) {
>>    $groups[ $element['id'] ][] =3D $element;
>> }
>>=20
>> var_dump( $groups );
>> ```
>>=20
>> This can now be achieved as follows (not preserving keys):
>>=20
>> ```
>> <?php
>> $array =3D [
>> [ 'id' =3D> 1, 'value' =3D> 'foo' ],
>> [ 'id' =3D> 1, 'value' =3D> 'bar' ],
>> [ 'id' =3D> 2, 'value' =3D> 'baz' ],
>> ];
>>=20
>> $groups =3D array_group( $array, function( $a, $b ) {
>> return $a['id'] =3D=3D $b['id'];
>> } );
>> ```
>>=20
>> 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.
>>=20
>> In any case, I think a utility function such as `array_group` will be =
widely useful.
>>=20
>> Please find attached a patch with a proposed implementation. Curious =
about your feedback.
>>=20
>> Best,
>>=20
>> Boro Sitnikovski
>>=20
>=20
> 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.

Folks did mention that RFC, but nobody mentioned the rejection reasons =
specifically. Thank you for the information and encouragement! I was a =
bit scared of this one being rejected too, but still decided to give it =
a shot :)=