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Date: Wed, 30 Mar 2022 09:26:50 -0500
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Subject: Re: [PHP-DEV] Undefined variables and the array append operator
From: larry@garfieldtech.com ("Larry Garfield")

On Wed, Mar 30, 2022, at 9:11 AM, Claude Pache wrote:
>> Le 29 mars 2022 =C3=A0 21:44, Rowan Tommins <rowan.collins@gmail.com>=
 a =C3=A9crit :
>>=20
>> Hi all,
>>=20
>> If $foo is not defined, statements such as $foo +=3D 1 and $foo .=3D =
'blah' raise "undefined variable" Warnings in PHP 8, and will throw Erro=
rs in PHP 9. However, the very similar looking $foo[] =3D 1 succeeds sil=
ently.
>>=20
>> This seems odd to me, as "append to string" and "append to array" see=
m like very similar operations, with most of the same use cases and poss=
ible bugs.
>>=20
>>=20
>
>
> Hi,
>
> There are various subcases to consider:
>
> (1) $x[] =3D 42; and $x['y'] =3D 42; where $x is undefined
>
> (2) $x[] =3D 42; and  $x['y'] =3D 42; where $x is null
>
> (3) $x['y'][] =3D 42;  and  $x['y']['w'] =3D 42; where $x is an array,=
 and=20
> $x['y'] is undefined.
>
> Of course, I agree that (1) should be an error.
>
> The case (3) is similar to (1), but I think it is more controversial t=
o=20
> change. I bet that they are various places in my code that take=20
> advantage of that feature, although personally I don=E2=80=99t mind to=
 write=20
> $x['y'] ??=3D [ ]; when needed.

We should probably also consider if there are other places where we're c=
omfortable with ??=3D working correctly.  I'm not sure off hand if it sh=
ould be acceptable in 1 or 2, but it's a question we should think throug=
h and document decisions on.

--Larry Garfield