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Date: Sun, 27 Feb 2022 10:59:35 +0100
To: internals@lists.php.net, Kamil Tekiela <tekiela246@gmail.com>
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Subject: =?US-ASCII?Q?Re=3A_=5BPHP-DEV=5D_Re=3A_Proposal_for_RFC_to_remove_und?= =?US-ASCII?Q?efined_array_index_warning_when_used_ina_ternary?=
From: mel@dafert.at (Mel Dafert)

On 27 February 2022 00:04:58 CET, Kamil Tekiela <tekiela246@gmail=2Ecom> wr=
ote:
>I just wanted to add that the following
>
>$name =3D $_POST['name'] ?: 'Default Name';
>
>with existence check would be
>
>$name =3D $_POST['name'] ?? null ?: 'Default Name';
>
>You don't need empty()=2E
>
>I would be against changing the behaviour of elvis/ternary operator=2E
>However, I remember seeing past suggestions to implement another operator=
=2E
>One that would fill the gap between null-coalesce and elvis operators=2E =
If I
>recall correctly, most of the time, these proposals end in consensus that
>such operator isn't really needed=2E See
>https://externals=2Eio/message/89292#89292 and
>https://externals=2Eio/message/101606#101610
>Maybe, it would be worthwhile to refresh a discussion about adding such
>operator to the PHP language?

I think that what would be needed here is another proposal from this discu=
ssion,
something like a null-safe operator but for array access=2E

From=20a different thread about this:

On 15 February 2022 16:50:48 CET, Rowan Tommins <rowan=2Ecollins@gmail=2Ec=
om> wrote:
>I seem to remember someone proposing an explicit operator for "this array=
 dimension might not exist", something like this:
>
>if ( $array[?'key'] =3D=3D=3D true )
>
>Which would translate to:
>
>if ( (array_key_exists('key', $array) ? $array['key'] : null) =3D=3D=3D t=
rue )

I would propose to extend this still to mean:
`if((($array !=3D=3D null && array_key_exists('key', $array)) ? $array['ke=
y'] : null) =3D=3D=3D true)`

This combines the above proposal with the behaviour of the nullsafe operat=
or
`?->`, allowing to signal that the array may be null or that the key may n=
ot be set=2E

This allows the requested functionality without warnings/notices:

$name =3D $_POST[?'name'] ?? 'Default Name';

But also allows accessing arrays with multiple, possibly defined dimension=
s:

$val =3D $array[?'a'][?'b'][?'c'] ?? 'default';

Currently, the last example would need to be a rather unwieldy ternary:

$val =3D (isset($array['a']) && isset($array['a']['b']) && isset($array['a=
']['b']['c']) ? $array['a']['b']['c'] : 'default';

The fact that the new syntax would also allow $array to be null may be und=
esirable in some cases, but I don't know if we can define the semantics in =
a better way=2E
(Also, in some cases this may actually be useful, eg=2E when mixing ?-> an=
d the new
[?=2E=2E=2E] syntax=2E)

I am not sure if the exact syntax/semantics proposed here are the best
solution, but I would argue that the fact that this seems to be a recurrin=
g topic
calls for a solution in that general direction=2E

Regards,
Mel