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Date: Fri, 19 Jul 2013 19:11:37 +0200
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To: Peter Cowburn <petercowburn@gmail.com>
Cc: Daniel Lowrey <rdlowrey@gmail.com>, "internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Language constructs and callability
From: jelle.zijlstra@gmail.com (Jelle Zijlstra)

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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 a=
nd
> > 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` a=
re
> > language constructs and not functions. I can see some potential benefit=
s
> > for working around this. For example, say I want to filter only the NUL=
L
> > 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 ni=
ce
> > 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 tha=
t
> > just a pipe dream that's not worth the implementation effort?
> >
>

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