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Date: Fri, 19 Jul 2013 18:07:30 +0100
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To: Daniel Lowrey <rdlowrey@gmail.com>
Cc: "internals@lists.php.net" <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Language constructs and callability
From: petercowburn@gmail.com (Peter Cowburn)

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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 benefits
> for working around this. For example, say I want to filter only the NULL
> 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');


>
> 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 chanc=
e
> of language constructs ever passing the tests for callability or is that
> just a pipe dream that's not worth the implementation effort?
>

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