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Date: Tue, 26 Nov 2013 12:54:07 -0500
Cc: Chris London <me@chrislondon.co>, Mats Lindh <mats.lindh@gmail.com>,
        "internals@lists.php.net" <internals@lists.php.net>
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To: Paul Dragoonis <dragoonis@gmail.com>
Subject: Re: [PHP-DEV] [Proposal] Modification to ?: functionality
From: john@bafford.com (John Bafford)


On Nov 26, 2013, at 12:41, Paul Dragoonis <dragoonis@gmail.com> wrote:

> On Tue, Nov 26, 2013 at 4:58 PM, Chris London <me@chrislondon.co> =
wrote:
>=20
>> On Tue, Nov 26, 2013 at 8:15 AM, Mats Lindh <mats.lindh@gmail.com> =
wrote:
>>=20
>>> On Tue, Nov 26, 2013 at 3:43 PM, Chris London <me@chrislondon.co> =
wrote:
>>>=20
>>>> I believe these two statements are functionally equivalent:
>>>>=20
>>>> $foo =3D $foo ? $foo : 'default';
>>>> $foo =3D $foo ?: 'default';
>>>=20
>>> They are.
>>>=20
>>> I would like to change it so it also checks for isset() so I propose =
the
>>>> following would be functionally equivalent:
>>>>=20
>>>> $foo =3D isset($foo) && $foo ? $foo : 'default';
>>>> $foo =3D $foo ?: 'default';
>=20
> We can't change the behaviour of ?: that ship has already sailed, =
we'll
> just be hurting existing codebases on upgrading and more user =
education is
> required to understand non-visual changes in syntax like this, lets =
try to
> learn from our mistakes by not changing 'behaviour' anymore.
>=20
> An alternative syntax that is similar and not ugly would be good since =
the
> ?: behaviour was broken from the start since you still need to run =
isset()
> before running ?: which was the problem we tried to solve in the first
> place but it just didn't happen.
>=20
> I don't like the @ symbol it's too different from what's already there =
on
> the ternary logic.
>=20
> Proposal:   $foo =3D $arr['value'] ?:: "";
>=20
> Thoughts?


What if it was:

$foo ?? $trueVal : $falseVal;

with the shortened form being:

$foo ??: $falseVal;

This would make the isset($foo) && $foo functionality available for the =
three operand version of ??:, and by making the ? the operator that's =
doubled in that case would make it more clear when reading as to what's =
going on (and maybe make it easier to parse?).

-John


>=20
>>=20
>>> The would break the assumption that a reference to an uninitialized =
value
>>> would generate a notice, unless explicitly handled in the logic.
>>>=20
>>> While I also would like to have something similar to ?: to handle =
default
>>> values for array keys, etc., this would change a fundamental =
assumption
>>> that as been in place for many years now. I'm not sure if that's a =
BC
>> break
>>> that would be acceptable this late. An alternative operator may be =
more
>>> suitable.
>>>=20
>>=20
>> What do you think about using:
>>=20
>> $foo =3D $foo @: 'default';
>>=20
>> and possibly
>>=20
>> $foo @=3D 'default';
>>=20
>>=20
>>=20
>>>=20
>>> The change proposed has also been discussed several times since the
>>> implementation of ?:. See the ifsetor-RFC:
>>>=20
>>> https://wiki.php.net/rfc/ifsetor
>>>=20
>>> It also contains links to the discussion around the feature back =
then.
>>>=20
>>> --mats