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Date: Fri, 19 Jul 2013 13:16:55 -0400
Message-ID: <CAH8MpnnjpSqXAymVBn0L=xP1of-SLoA01VOxCfVV5r1Gs4X-FA@mail.gmail.com>
To: Jelle Zijlstra <jelle.zijlstra@gmail.com>
Cc: Peter Cowburn <petercowburn@gmail.com>, 
	"internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Language constructs and callability
From: rdlowrey@gmail.com (Daniel Lowrey)

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> Oh yeah, I see your point about is_null but not why it makes any more
sense to allow language constructs there.

Yeah I don't know if it even does. I'm not even really sure if there's a
good example use case for it besides the array_filter/isset combo. My
question was really only exploratory in nature.


On Fri, Jul 19, 2013 at 1:12 PM, Peter Cowburn <petercowburn@gmail.com>
 wrote:

> Oh yeah, I see your point about is_null but not why it makes any more
> sense to allow language constructs there.
>


On Fri, Jul 19, 2013 at 1:11 PM, Jelle Zijlstra <jelle.zijlstra@gmail.com>w=
rote:

>
>
>
> 2013/7/19 Peter Cowburn <petercowburn@gmail.com>
>
>> On 19 July 2013 17:36, Daniel Lowrey <rdlowrey@gmail.com> wrote:
>>
>> > I have a simple question about the callability of language constructs
>> and
>> > whether or not that's something that might change in the future.
>> Consider:
>> >
>> > var_dump(is_callable('echo')); // bool(false)
>> > var_dump(call_user_func('echo', 'foo')); // E_WARNING
>> > echo('foo'); // foo
>> >
>> > var_dump(is_callable('isset')); // bool(false)
>> > var_dump(isset(1)); // E_ERROR
>> >
>> > Obviously this behavior arises because tokens like `echo` and `isset`
>> are
>> > language constructs and not functions. I can see some potential benefi=
ts
>> > for working around this. For example, say I want to filter only the NU=
LL
>> > elements from an array but keep the other "falsy" values. Recognizing
>> > `isset` as callable would allow me to do this:
>> >
>> > var_dump(array_filter([0, FALSE, NULL], 'isset')); // [0, FALSE]
>> >
>>
>> array_filter([=85], 'is_null');
>>
>> That would do the opposite of what you want.
>
>>
>> >
>> > Of course, this limitation is trivial to work around with a userland
>> > callback to check for the explicit NULL equivalency, but it would be
>> nice
>> > to avoid the hassle. So my question is ...
>> >
>> > How deeply ingrained into the engine is this behavior? Is there any
>> chance
>> > of language constructs ever passing the tests for callability or is th=
at
>> > just a pipe dream that's not worth the implementation effort?
>> >
>>
>
>

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