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Date: Sat, 11 Nov 2023 20:43:00 +0100
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To: David Gebler <davidgebler@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Array functions with strict comparison
From: andreas@dqxtech.net (Andreas Hennings)

Hello David,

On Sat, 11 Nov 2023 at 20:04, David Gebler <davidgebler@gmail.com> wrote:
>
> On Sat, Nov 11, 2023 at 6:05=E2=80=AFPM Andreas Hennings <andreas@dqxtech=
.net>
> wrote:
>
> > Hello internals,
> > I noticed that array functions like array_diff(), array_intersect()
> > etc use weak comparison.
> >
> >
> That's not quite correct. Using the example of array_diff, the comparison
> is a strict equality check on a string cast of the values. So
> array_diff([""], [false]) will indeed be empty
> but array_diff(["0"],[false]) will return ["0"].

Thanks, good to know!
So in other words, it is still some kind of weak comparison, but with
different casting rules than '=3D=3D'.
Still this is not desirable in many cases.

>
> Tbh any use case for whatever array function but with strict comparison i=
s
> such an easy thing to implement in userland[1] I'm not bothered about
> supporting it in core. But that's just me. I don't generally like the ide=
a
> of adding new array_* or str_* functions to the global namespace without
> very good cause. There is a precedent for it though, in terms of changes
> which have gone through in PHP 8, such as array_is_list or str_starts_wit=
h.


I would argue that the strict variants of these functions would be
about as useful as the non-strict ones.
Or in my opinion, they would become preferable over the old functions
for most use cases.

In other words, we could say the old/existing functions should not
have been added to the language.
(of course this does not mean we can or should remove them now)

Regarding performance, I measure something like factor 2 for a diff of
range(0, 500) minus [5], comparing array_diff() vs array_diff_strict()
as proposed here.
So for large arrays or repeated calls it does make a difference.

Regarding the cost of more native functions:
Is the concern more about polluting the global namespace, or about
adding more functions that need to be maintained?
I can see both arguments, but I don't have a clear opinion how these
costs should be weighed.

Cheers
Andreas



>
> [1] Example:
>
> function array_diff_strict(array $array1, array ...$arrays): array
>     {
>         $diff =3D [];
>         foreach ($array1 as $value) {
>             $found =3D false;
>             foreach ($arrays as $array) {
>                 if (in_array($value, $array, true)) {
>                     $found =3D true;
>                     break;
>                 }
>             }
>             if (!$found) {
>                 $diff[] =3D $value;
>             }
>         }
>         return $diff;
>     }