[RFC] Change behaviour of array sort functions to return a copy of the sorted array

Hello internals,

I would like to propose a short RFC to make the return value of the sort() and similar functions more useful:
https://wiki.php.net/rfc/array-sort-return-array

I intend for the discussion to last 2 weeks and then open the vote.

Best regards,

Gina P. Banyard

Hey Gina,

Just to make sure I understand (the RFC isn't 100% clear on this), but this is still an in-place modification, just returning it as well. Such that

$copy = sort($original);
assert($copy === $original);

??

— Rob

Hi Gina

I would like to propose a short RFC to make the return value of the sort() and similar functions more useful:
https://wiki.php.net/rfc/array-sort-return-array

I think this adds two unnecessary sources of confusion:

1. What Rob already mentioned: Users may look at the signature and see
   that an array is returned, and assume the argument won't get modified.

2. Is the array returned by value or by reference? I.e.

$a = [...];
$b = &sort($a);
$b[] = 'foo';
// Does $a get modified?

You're mentioning that:

This behaviour is annoying as it makes writing code in a functional way more cumbersome and tedious.

It would help if there were some examples. In any case, I don't think
by-ref functions are particularly "functional" anyway.

Ilija

Hello internals,

I would like to propose a short RFC to make the return value of the
sort() and similar functions more useful:
https://wiki.php.net/rfc/array-sort-return-array

I intend for the discussion to last 2 weeks and then open the vote.

Best regards,

Gina P. Banyard

Like others, I'm skeptical of the behavior here not being all that clear.

What several other languages do, and what I have in the plan for collections if/when they ever happen, is sort() sorts in place, while sorted() returns a new value. There's similarly reverse() (in place) and reversed() (new value returned).

*sorted($arr) seems like it would be a lot less confusing, and consistent with what other languages (and hopefully future PHP) do. (I don't know what that means for array_walk(), but I don't know what that would even return anyway.)

--Larry Garfield

Hello internals,

I would like to propose a short RFC to make the return value of the sort()
and similar functions more useful:
https://wiki.php.net/rfc/array-sort-return-array

I intend for the discussion to last 2 weeks and then open the vote.

Best regards,

Gina P. Banyard

I like this RFC because I have a distaste for any function/method that
always returns a single value -- the return value indicates nothing usable.
I also find that I prefer to avoid array_walk() because I can't elegantly
nest it in other function calls or return/print the traversed data.

Might the transition be simpler if the naming convention is standardized to
have array_ meaning "returns the input [sorted|shuffled|traversed] array"
and without the prefix means "modify by reference"?

That naming convention will not look absurd among other native array_
functions and prefix-trimmed functions will afford developers to continue
using the original modify by reference behavior (if they have performance
or memory reasons).

| returns copy of array | by reference |
| ---------------------- |---------------- |
| array_sort() | sort() |
| array_rsort() | rsort() |
| array_asort() | asort() |
| array_arsort() | arsort() |
| array_ksort() | ksort() |
| array_krsort() | krsort() |
| array_natsort() | natsort() |
| array_natcasesort() | natcasesort() |
| array_usort() | usort() |
| array_uasort() | uasort() |
| array_uksort() | uksort() |
| array_multisort() | multisort() |
| array_shuffle() | shuffle() |
| array_walk() | walk() |
| array_walk_recursive() | walk_recursive() |

Good luck regardless,
mickmackusa

Hello internals,

I would like to propose a short RFC to make the return value of the sort() and similar functions more useful:
https://wiki.php.net/rfc/array-sort-return-array

I intend for the discussion to last 2 weeks and then open the vote.

Best regards,

Gina P. Banyard
I've been working up something very much similar so I'd be well behind this.

My thinking ended up the same as Larry Garfield's:

*sorted($arr) seems like it would be a lot less confusing, and
consistent with what other languages (and hopefully future PHP) do. (I
don't know what that means for array_walk(), but I don't know what that
would even return anyway.)

Making it a new function instead of changing the existing function would
be less of a break it seems.

Excerpts from my drafts:

All of the functions [the thirteen array sorting functions, including
shuffle()] have the less-than-informative return type of true (except
array_multisort() with its more complex argument requirements and
hence the ability to also return false). All of their behaviour is by
reference. Oh, except when they flat-out fail, in which case they return
null.

This means that if you want to sort an array you have to have an entire
statement devoted to the task. As an expression, sort() just doesn’t
compose: you can’t sensibly use it anywhere as part of a larger expression.
You have to write:
$escaped = $array->valued($expression);
sort($escaped);
$escaped = array_map(escape(...), $escaped);
because
$escaped = array_map(escape(...), sort($array->valued($expression));
simply won’t work.
It gets in the way when using it as a callback in array functions. You
can’t use:
$sorted_datasets = array_map(sort(...), $datasets);
You want
$sorted_datasets = $datasets;
array_walk($sorted_datasets, sort(...));
array_walk() is the only built-in array function using callbacks that
can meaningfully accept sort() (even the array_walk_recursive()
variant will recurse into child arrays instead of sorting them). Because
array_walk() iterates through the array by reference as well, it too
interrupts functional composition, as just shown above. But at least it
can often be replaced by array_map() (just look at the number of user
notes on its manual page that suggest using references to make it behave
more that way). array_walk() is basically for the case where there is
no useful value to return from traversing the array (good thing, too,
since its return type is true). But I digress.

...

The name sorted() has already been introduced. The -ed suffix can be
grammatically applied to all of the sorting functions (technically for
shuffle() the suffix would be -d because the e is already there).
But that is just the one I came up with.
What we don’t want is Yet Another Prefix to go into the alphabet soup
that is ([ak]?r?|u[ak]?|nat(case)?). “Hey, how about we use ‘f’ as a
prefix meaning ‘functional’?” “Do you want to be responsible for
prefixing ‘uksort’ with an ‘f’?”
At the same time we don’t want any modification that would make the name
clunky to use. Not everything should be reliant on IDE autocompletion.

...

Most languages in widespread use do operate on their arrays in place,
but in those cases the arrays are object types and sorting is an
instance method performed on and modifying the object. That’s not how
PHP models arrays. Functional languages meanwhile have – by definition –
functional sort functions.
One notable example is Python, in which lists have an in-place .sort()
method. The language however also offers a global sorted() function,
which takes a list and returns a new, sorted one, pretty much like what
is proposed here, and for pretty much the same reason: it is more easily
composable with other operations.

...

It would impact anyone (such as myself) who already defines global
functions named sorted(). In my case it’s precisely so that I can have
such functional sort functions. It’s not unlikely that there are
functions with that name that have other jobs (e.g. a sorted that
tests whether a list is sorted) and would need to be renamed (e.g. to
is_sorted). But adding any functions to core would mean renaming
existing global user functions that currently have the same names
regardless of what they are for. A quick github search turned up a
number of sorted global functions, some of them exactly matching the
userland implementation above; and all (from the sample I took) looking
like the intent is to take an array (by value) or something that is
queried for an array, sort it in some way, and return the result. In
other words, passing the array to be sorted by value and returning the
sorted array is the more common idiom.

[The userland implementation mentioned being

function sorted(array $array): array
{
sort($array);
return $array;
}

]

Hello internals,

I would like to propose a short RFC to make the return value of the sort() and similar functions more useful:
https://wiki.php.net/rfc/array-sort-return-array

I am going to respond out of threads.

This RFC does NOT change the by-ref parameter passing NOR the in-place sorting of these functions.
I don't see why people are thinking this would be changed, as I only ever talk about the return value.
But I added a sentence in the Unaffected PHP Functionality section.

I really struggle to see the benefit of introducing new functions that would do the exact same thing as this RFC,
except the in-place modification, as seen by the already existing bikesheeding on function naming.

For an example, I'm going to pull out my solution to day 1 of the 2022 advents of code:

https://github.com/Girgias/advent-of-code/blob/19283e1f5ef503c8a4478e58aaa57ff2fb7164c7/2022/01/puzzle.php#L25

If we had a pipe operator, or if decided to write this less legible with nested calls, it would like this:

$elves = array_map(
'array_sum',
array_map(
fn($v) => explode("\n", $v),
explode(
"\n\n",
$input
)
)
);
rsort($elves);
$top3 = array_slice($elves, 0, length: 3);

However, if the sort functions would return a useful value instead of true I could chain it together completely as follows:

$top3 = array_slice(
rsort(
array_map(
'array_sum',
array_map(
fn($v) => explode("\n", $v),
explode(
"\n\n",
$input
)
)
)
),
0,
length: 3
);

In either case, the fact the array is sorted in place is something I don't care, as it is just a temporary step.
However, in the current state, I need to stop chaining function calls just to be able to get the sorted array that I am going to process and discard at the next function call.

This type of data processing pattern can be generalized to any collection of data that needs to be sorted/filtered and processed upon.

This RFC is "just" making the return value of these functions useful.

Would a "proper" functional variant of these functions which do not take the input argument by reference be useful? Yes.
Is this completely orthogonal to the point of this RFC? Also yes.

Best regards,

Gina P. Banyard

I would like to propose a short RFC to make the return value of the sort() and similar functions more useful:
https://wiki.php.net/rfc/array-sort-return-array

After having thought a bit about
https://github.com/php/php-src/issues/16648, I don't think it makes
much sense to stick a band-aid on our sorting functions to make them
more functional. Instead we should better introduce proper functional
functions which do not modify the given array. Less efficient, but that
often may not matter in practise.

Christoph