RFC [Discussion] array_column results grouping

Gonna vote no on this: please design new/dedicated functions, rather than
expanding optional parameters.

Hello, this is a proposal to upgrade the functionality of
array_column to return an indexed array for all of the matched data
instead of a single result.

the RFC had been created here
https://wiki.php.net/rfc/array_column_results_grouping and the PR is
in here https://github.com/php/php-src/pull/7698.

However, I am not sure, if we need to add a fourth parameter to the
function to change its behavior or we can add it as a new function,
something like array_column_group or any other name.

Regards,
Hassan.

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Hello, this is a proposal to upgrade the functionality of
array_column to return an indexed array for all of the matched data
instead of a single result.

the RFC had been created here
https://wiki.php.net/rfc/array_column_results_grouping and the PR is
in here https://github.com/php/php-src/pull/7698.

However, I am not sure, if we need to add a fourth parameter to the
function to change its behavior or we can add it as a new function,
something like array_column_group or any other name.

Hai Hassan.

It seems that your proposal is just save no more than 3 lines compared with
foreach. Moreover, foreach can do better than your version.

foreach ($persons as $p) {
    $groups[$p["education"]][$p["sex"]][MORE_SUBGRUP][] = $p;
}

output:

$groups = [
    "elementary" => [
        "female" => [
            MORE_SUBGRUP_1 => [
                0 => [...],
                1 => [...]
            ],
            MORE_SUBGRUP_2 => [
                0 => [...],
                1 => [...]
            ],
            ...
        ],
        "male" => [
            MORE_SUBGRUP_1 => [
                0 => [...],
                1 => [...]
            ],
            MORE_SUBGRUP_2 => [
                0 => [...],
                1 => [...]
            ],
            ...
        ],
    ],
    "highschool" => [
        ...
    ],
    ...
];

my suggestions are:

• don't limit to array => involve object as well
• offer reducer callable as an optional last param.

reducer callable it will transform 2 steps algo (populating the groups and then
reducing) to become a single step. but if it is not provided, the function
returns the member of the group (same as example above).

old way:

// step-1
$group = [];
foreach ($persons as $p) {/*...*/}

// step-2
foreach ($group as &$eduGroup) {
    foreach ($eduGroup as &$sexGroup) {
        $sumWeight = 0;
        foreach ($sexGroup as $item) {
            $sumWeight += $item->weight;
        }
        $sexGroup = $sumWeight / count($sexGroup);
    }
}

output:

$groups = [
    "elementary" => [
        "female" => 40,
        "male" => 50,
    ],
    "highschool" => [
        "female" => 60,
        "male" => 65,
    ],
    ...
];

new way:

array_column_group(
    $group,
    ["education", "sex", MORE_SUBGRUP],
    fn ($item, $i, $cumm) => ($item->weight + ($cumm * $i)) / ($i + 1)
);

the signature:

// array_column_group signature
array_column_group(
    array|object $array,
    int|string|array $index_key,
    callable $reducer = null
)

// callable signature
fn (array|object $item, int|string $index, mixed $cummulative): mixed

note:

• $index_key can be in the form ["education", ...] or "education".
• or even [0, 1, ...] or 0.

So virtually, array_column_group is a hybrid between array_column and
array_walk (or other function with a funny name which I don't remember).

Best Regards
Hendra Gunawan.

Hello Folks, Thanks a lot for your feedback, as already mentioned in
the RFC and as mentioned by Rowan too a new function is an option. I
think that mostly we will go with the new function option.
I will try to edit the PR to add a new function, does there any
suggestions/naming conventions for the new function? a colleague
suggested being array_group_by and Hendra already suggested to be
array_column_group which is good too.

Regards,
Hassan

Gonna vote no on this: please design new/dedicated functions,
rather than
expanding optional parameters.

I would vote no for the same reason.

Since this is explicitly an open question in the current RFC draft, it
seems a bit premature to talk about voting, rather than encouraging the
RFC to develop in a particular direction.

For what it's worth, I agree that a new function is probably better
here, because the argument list of array_column is already quite
complicated. A new function also leaves the way open to add more
functionality, such as the "reducer" callback suggested by Hendra
Gunawan; I don't think that's needed in the first implementation, though.

In general, I like the proposal - like array_column itself, it's one of
those things that's fairly simple to do in userland, but also fairly
often done, so compacting it to a neat function call seems useful.

Regards,

--
Rowan Tommins
[IMSoP]

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Since this is explicitly an open question in the current RFC draft, it
seems a bit premature to talk about voting, rather than encouraging the
RFC to develop in a particular direction.

I hope it was taken as nothing more than an indication that adding an
extra argument to array_columns would not be our preference for the
route to go down :-)

I could see the benefits to a standalone array_column_group function,
that way the expected dimensions of the output would be more easily
recognisable without having to inspect the parameters.

As this RFC focuses heavily on array_columns, including all of the
examples and the PR, I would encourage the author to consider an RFC
specifically for array_column_group.

Mark Randall