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Date: Thu, 6 Apr 2023 12:18:50 +0200
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Subject: Re: [PHP-DEV] Array spread append
From: tovilo.ilija@gmail.com (Ilija Tovilo)

Hi Michael

> I would like to open a discussion for https://github.com/php/php-src/issu=
es/10791 .
> [https://opengraph.githubassets.com/a23cb565cc8acac6a33ecab5d9ee68a46f046=
a1ffe215501673156e506695430/php/php-src/issues/10791]<https://github.com/ph=
p/php-src/issues/10791>
> Array spread append =C2=B7 Issue #10791 =C2=B7 php/php-src<https://github=
.com/php/php-src/issues/10791>
> Description Currently spread operator can be used for almost anything. Bu=
t not for array append. I propose the following to be supported: <?php $arr=
 =3D [1, 2]; $arr2 =3D [3, 4]; $arr[...] =3D $arr2; // ...
> github.com
> Appending N elements to an array is quite common language usage pattern a=
nd I belive it should be supported natively for shorter syntax, language co=
nsistency and performance.Hi Michael

There are a few questions that come to mind (there may be more).

* Are integer keys preserved? I'm assuming no, as otherwise it would
be the same as `$a + $b`.
* What is the return value of the expression `$a[...] =3D $b`? I'm
assuming $a after the additions of $b?
* How does it behave in combination with `ArrayAccess`? Throw? Call
`offsetSet` for each element?
* How does it interact with references? E.g. This is valid PHP code:
`assign_by_ref($a[])` (https://3v4l.org/qoJYn)
* How does it interact with undefined/null values? E.g. `$a[] =3D 42;`
works without declaring $a first.
* Is there a need for this? Given that `+` doesn't work with
sequential lists and `array_push($a, ...$b)` doesn't work with strings
I'd say possibly. `[...$a, ...$b]` works but requires duplication of
the array which in loops can be detrimental to performance.

Ilija