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Date: Tue, 26 Nov 2013 12:57:27 -0500
Message-ID: <CABDNdAGKZGvk76jgqjNvwmOvKsvvSkYsTeWoqtirqctn6KPmtA@mail.gmail.com>
To: Paul Dragoonis <dragoonis@gmail.com>
Cc: Chris London <me@chrislondon.co>, Mats Lindh <mats.lindh@gmail.com>, 
	"internals@lists.php.net" <internals@lists.php.net>
Content-Type: text/plain; charset=ISO-8859-1
Subject: Re: [PHP-DEV] [Proposal] Modification to ?: functionality
From: pjsturgeon@gmail.com (Philip Sturgeon)

On Tue, Nov 26, 2013 at 12:41 PM, Paul Dragoonis <dragoonis@gmail.com> wrote:
> On Tue, Nov 26, 2013 at 4:58 PM, Chris London <me@chrislondon.co> wrote:
>
>> On Tue, Nov 26, 2013 at 8:15 AM, Mats Lindh <mats.lindh@gmail.com> wrote:
>>
>> > On Tue, Nov 26, 2013 at 3:43 PM, Chris London <me@chrislondon.co> wrote:
>> >
>> >> I believe these two statements are functionally equivalent:
>> >>
>> >> $foo = $foo ? $foo : 'default';
>> >>
>> >> $foo = $foo ?: 'default';
>> >>
>> >
>> > They are.
>> >
>> >
>> > I would like to change it so it also checks for isset() so I propose the
>> >> following would be functionally equivalent:
>> >>
>> >> $foo = isset($foo) && $foo ? $foo : 'default';
>> >>
>> >> $foo = $foo ?: 'default';
>> >>
>>
>
> 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.
>
> 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.
>
> I don't like the @ symbol it's too different from what's already there on
> the ternary logic.
>
> Proposal:   $foo = $arr['value'] ?:: "";
>
> Thoughts?
>
>>
>> > The would break the assumption that a reference to an uninitialized value
>> > would generate a notice, unless explicitly handled in the logic.
>> >
>> > 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.
>> >
>>
>> What do you think about using:
>>
>> $foo = $foo @: 'default';
>>
>> and possibly
>>
>> $foo @= 'default';
>>
>>
>>
>> >
>> > The change proposed has also been discussed several times since the
>> > implementation of ?:. See the ifsetor-RFC:
>> >
>> > https://wiki.php.net/rfc/ifsetor
>> >
>> > It also contains links to the discussion around the feature back then.
>> >
>> > --mats
>> >
>>

This seems like a cracking time to suggest:

   $x ||= $y;

The difference? Anything left of the ? SHOULD fail if it is not set,
because you are using it in a condition which is dangerous and odd for
other types of condition, but adding in this new syntax (similar to
Ruby) would essentially evaluate to this:

   empty($x) ? $y : $x;

This gives keeps the behavior of ternary operators working in the same
way, but adds what we want: the ability to nicely set defaults for
variables and array keys that may not be set.