Re: [PHP-DEV] [RFC] Implicit isset() in Shorthand Ternary Operator

On 8 Sep 2014, at 09:06, Michael Wallner <[email protected]> wrote:

> On 07/09/14 14:25, Andrea Faulds wrote:
>> 
>> On 7 Sep 2014, at 13:22, Sherif Ramadan <[email protected]>
>> wrote:
>> 
>>> 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.
>> 
>> There’s actually a quite serious issue just now, which is that it
>> evaluates the first operand twice if it’s 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’d happen twice. This is
>> obviously not good, and I’m going to figure out how to fix this.
>> 
> 
> This could very well be the reason why it is like it is today.

I doubt it, it’s possible to avoid double-evalution, and I don’t think it’s 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 <[email protected]> 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 
> 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’t really like the idea. It’s too similar to ?: so I don’t think it’d be accepted, and even if it was, I’m not sure we really need another operator. I’d 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 <[email protected]> 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.
> 
> I think, the notice is really valuable when accessing the value and doing something with it - like myFunction($_GET['not_set']), but if you're just checking for the existence, I, too, think it is more annoying. My way was to suppress it by adding the silence-operator ;)
> 
> I always used like:
> @$_GET['mykey'] ?: ””

The silence operator is bad for three reasons. First, it’s very slow, having a significant performance impact. Second, @ silences not only innocuous E_NOTICEs, but *all* errors, even very serious ones. That’s not good. The third is that it interacts with some error handlers badly, or so I’ve 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’d be able to do foo()[0] ?: $bar and foo() would only be called once) and because with the full-length ternary operator, it wouldn’t really help you much: $_GET[‘foo’] ? $_GET[‘foo’] : ‘blah’ isn’t much shorter than the version with explicit isset.

--
Andrea Faulds
http://ajf.me/