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Date: Mon, 8 Sep 2014 14:58:17 +0100
Cc: Sherif Ramadan <theanomaly.is@gmail.com>,
 Pierre Joye <pierre.php@gmail.com>,
 PHP internals <internals@lists.php.net>
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To: Michael Wallner <mike@php.net>,
 Shashank Kumar <shashankkumar.me@gmail.com>,
 Simon Schick <simonsimcity@gmail.com>
Subject: Re: [PHP-DEV] [RFC] Implicit isset() in Shorthand Ternary Operator
From: ajf@ajf.me (Andrea Faulds)


On 8 Sep 2014, at 09:06, Michael Wallner <mike@php.net> wrote:

> On 07/09/14 14:25, Andrea Faulds wrote:
>>=20
>> On 7 Sep 2014, at 13:22, Sherif Ramadan <theanomaly.is@gmail.com>
>> wrote:
>>=20
>>> I've played around with this branch for a bit and seems reasonable,
>>> passes the tests, and doesn't seem to have any serious
>>> issues/memories leaks AFAICT.
>>=20
>> There=92s actually a quite serious issue just now, which is that it
>> evaluates the first operand twice if it=92s not empty. This is =
because
>> $a ?: $b is expanded to empty($a) ? $b : $a, such that if you did
>> something which mutates state in there, it=92d happen twice. This is
>> obviously not good, and I=92m going to figure out how to fix this.
>>=20
>=20
> This could very well be the reason why it is like it is today.

I doubt it, it=92s possible to avoid double-evalution, and I don=92t =
think it=92s terribly difficult. I just did things the easy way and it =
turns out that has problems.


On 8 Sep 2014, at 13:04, Shashank Kumar <shashankkumar.me@gmail.com> =
wrote:

> Rather than giving a new meaning to an old operator why not have a =
different operator for this?
> .NET has a 'null coalescing' operator for the same purpose which works =
out quite well in the given situation=20
> and is non-ambiguous as well.
> http://msdn.microsoft.com/en-us/library/ms173224.aspx

We could add such an operator, perhaps with the ?? syntax. However, I =
don=92t really like the idea. It=92s too similar to ?: so I don=92t =
think it=92d be accepted, and even if it was, I=92m not sure we really =
need another operator. I=92d much rather just make ?: do what, IMO, is =
the right thing and what it always should have done.

On 8 Sep 2014, at 08:58, Simon Schick <simonsimcity@gmail.com> wrote:

> I feel more like Sherif Ramadan. Even so I've quite often been in the =
same situation, I don't think it's a good solution to change something =
like that, just for the shorthand-operator.
>=20
> I think, the notice is really valuable when accessing the value and =
doing something with it - like myFunction($_GET['not_set']), but if =
you're just checking for the existence, I, too, think it is more =
annoying. My way was to suppress it by adding the silence-operator ;)
>=20
> I always used like:
> @$_GET['mykey'] ?: =94=94

The silence operator is bad for three reasons. First, it=92s very slow, =
having a significant performance impact. Second, @ silences not only =
innocuous E_NOTICEs, but *all* errors, even very serious ones. That=92s =
not good. The third is that it interacts with some error handlers badly, =
or so I=92ve heard.

> I can't come up with a good mid-way right now, but I don't think it's =
a good way to change this ONLY for the short-hand operator.

Actually, there is a case for doing it for $a ?: $b and not $a ? $a : =
$b, in that it could avoid double evaluation (you=92d be able to do =
foo()[0] ?: $bar and foo() would only be called once) and because with =
the full-length ternary operator, it wouldn=92t really help you much: =
$_GET[=91foo=92] ? $_GET[=91foo=92] : =91blah=92 isn=92t much shorter =
than the version with explicit isset.

--
Andrea Faulds
http://ajf.me/