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Date: Fri, 4 May 2012 14:18:03 -0700
Message-ID: <CAKOpQSxoN5rKbhnE-b-UEwCJ7LU4d1uno6OWEnFRXacwXjt6Ug@mail.gmail.com>
To: Ferenc Kovacs <tyra3l@gmail.com>
Cc: Richard Lynch <ceo@l-i-e.com>, PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] [RFC] Allow non-variable arguments to empty() and isset()
From: kris.craig@gmail.com (Kris Craig)

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On Fri, May 4, 2012 at 1:27 PM, Ferenc Kovacs <tyra3l@gmail.com> wrote:

>
>> I've been following the debate and I'm still a bit unclear as to what the
>> benefit would be to allowing non-variables in isset().  I mean, as was
>> stated earlier, expressions are neither "set" nor "unset".  Furthermore,
>> if
>> you were to assign a variable to any valid expression (empty or
>> otherwise),
>> it would be considered "set".  Therefore, through simple deductive logic,
>> would an expression passed to isset() not, by definition, *always* return
>>
>> TRUE if the expression itself is syntactically valid?
>>
>
> yeah, this wouldn't be much to think about if isset in php wouldn't handle
> null values as not set.
>

Hmm I'd never really thought about that before.  But now that you mention
it, that does sound like a problem.  Honestly, I can see no value in
maintaining a different "standard" for what constitutes a set or not-set
variable depending on the function.  While I understand Pierre's point that
people have used $var = NULL; in the past to unset variables, I don't think
we should actually be supporting that.  After all, $var = (anything,
including nothing) is, by definition, "setting" the variable to something
(or nothing).

I would analogize this to a printed dictionary.  Let's say you look up the
word, "glarbofatass".  It's not there.  So you take out another dictionary
and look it up again.  There's an entry for it, but the entry says, "This
word has no meaning."  In the first dictionary, "glarbofatass" is not set.
 In the second dictionary, "glarbofatass" is set to the state of having no
meaning.  Nevertheless, it *is* set.

I've never thought of setting something to NULL as being *literally *the
same thing as unsetting it (though the purpose and end result are mostly
the same).  If we didn't have an unset() function, I might feel differently
about this.  But we do, so really I don't see why "= NULL" needs to be an
alias for unset().  To be honest, I doubt this would pose any real BC
breakage, either, unless someone can point me to an instance where somebody
uses "= NULL" to unset a variable and then checks it with isset() later,
expecting FALSE.

Personally, I would consider "= NULL" == unset() but only as it pertains to
isset() to be a bug that should be fixed, not a "feature" that should be
preserved.  And if we make that change (perhaps target it for PHP 6 since
it would nonetheless pose a fundamental logic change, albeit an extremely
minor and low-impact one), then this RFC suddenly makes a lot more sense
while allowing the scope to be limited to empty() without creating any
annoying contradictions.

--Kris

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