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[PHP-DEV] [RFC] Allow non-variable arguments to empty() and isset()

Posted by Nikita Popov 
Hi internals!

As per the comments I created an RFC, proposing to allow arbitrary
expressions to be passed to empty() and isset():

https://wiki.php.net/rfc/empty_isset_exprs

The patch is available as a PR:

https://github.com/php/php-src/pull/54

Nikita

PS: I added isset() too, to address the consistency concerns mentioned on IRC.

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On Thu, Apr 12, 2012 at 2:42 PM, Nikita Popov <[email protected]>wrote:

>
> As per the comments I created an RFC, proposing to allow arbitrary
> expressions to be passed to empty() and isset():
>
> https://wiki.php.net/rfc/empty_isset_exprs
>
> The patch is available as a PR:
>
> https://github.com/php/php-src/pull/54
>
> Nikita
>
> PS: I added isset() too, to address the consistency concerns mentioned on
> IRC.
>
> Just to be clear, under the new behavior, calling "empty" or "isset" on
undefined variables and undefined array indices shouldn't produce a notice
when E_NOTICE is set, correct? Basically, the change isn't regressive.

<?php
error_reporting(E_ALL);
echo empty($foo) ? "\$foo isn't set\n" : "foo: $foo\n";
# result: "$foo isn't set", and no "Undefined variable" notice.

From my reading of the patch this is true, but I want to make sure I'm not
missing something. If this is so, how about adding appropriate regression
tests to empty_with_expr.phpt and empty_with_isset.phpt?
On Fri, Apr 13, 2012 at 12:42 AM, Galen Wright-Watson
<[email protected]> wrote:
> Just to be clear, under the new behavior, calling "empty" or "isset" on
> undefined variables and undefined array indices shouldn't produce a notice
> when E_NOTICE is set, correct? Basically, the change isn't regressive.
Yup, that's right. So the change is BC-safe :)

> If this is so, how about adding appropriate regression
> tests to empty_with_expr.phpt and empty_with_isset.phpt?
The normal empty()/isset() behavior (including the suppression of the
notice) is tested in a few other tests, that's why I didn't add
additional tests for it there :)

Nikita

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Hi,

2012/4/12 Nikita Popov <[email protected]>:
> PS: I added isset() too, to address the consistency concerns mentioned on IRC.

I would have voted +1 if it didn't contain the isset() change. None of
the examples used in the isset_with_expr.phpt test seems logic to me.

Care to explain the consistency concerns here?

Patrick

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On Mon, Apr 30, 2012 at 9:50 AM, Patrick ALLAERT <[email protected]> wrote:
> Hi,
>
> 2012/4/12 Nikita Popov <[email protected]>:
>> PS: I added isset() too, to address the consistency concerns mentioned on IRC.
>
> I would have voted +1 if it didn't contain the isset() change. None of
> the examples used in the isset_with_expr.phpt test seems logic to me.
>
> Care to explain the consistency concerns here?
The concerns came from laruence, so maybe he could drop a comment here
:) Basically, empty() and isset() are very similar in their nature, so
changing only one of them might seem inconsistent.

Personally I don't see much use in allowing expressions in isset().
People being confused by empty(trim($_GET['foo'])) not working is
quite common, but I've never heard of somebody trying to use isset()
on a function call. The name already makes clear that it's intended
for use on variables.

So, I'm not quite sure what I'm supposed to do about this. Should I
add two vote options, one for empty() only, one for both?

Nikita

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On Mon, Apr 30, 2012 at 9:50 AM, Patrick ALLAERT <[email protected]> wrote:
> Hi,
>
> 2012/4/12 Nikita Popov <[email protected]>:
>> PS: I added isset() too, to address the consistency concerns mentioned on IRC.
>
> I would have voted +1 if it didn't contain the isset() change. None of
> the examples used in the isset_with_expr.phpt test seems logic to me.
>
> Care to explain the consistency concerns here?
>
> Patrick

I changed the vote to have three options: "Both empty() and isset()",
"Only empty()" or "None"

https://wiki.php.net/rfc/empty_isset_exprs#vote

Nikita

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hi,

On Mon, Apr 30, 2012 at 3:05 PM, Nikita Popov <[email protected]> wrote:

> I changed the vote to have three options: "Both empty() and isset()",
> "Only empty()" or "None"
>
> https://wiki.php.net/rfc/empty_isset_exprs#vote

Please post a top thread to notice everyone about this new vote with a
short explanation.

Yes, I told you that on IRC a good dozen times since you sent this
mail here, but there are good reasons why we do so. For one, many do
not follow any single thread on internals and I would not have noticed
that mail if I was not on IRC today. So please do it, or the votes
result, no matter the outcome, cannot be accepted.

Thanks for your understanding,
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On Mon, Apr 30, 2012 at 2:39 PM, Nikita Popov <[email protected]>wrote:

> On Mon, Apr 30, 2012 at 9:50 AM, Patrick ALLAERT <[email protected]>
> wrote:
> > Hi,
> >
> > 2012/4/12 Nikita Popov <[email protected]>:
> >> PS: I added isset() too, to address the consistency concerns mentioned
> on IRC.
> >
> > I would have voted +1 if it didn't contain the isset() change. None of
> > the examples used in the isset_with_expr.phpt test seems logic to me.
> >
> > Care to explain the consistency concerns here?
> The concerns came from laruence, so maybe he could drop a comment here
> :) Basically, empty() and isset() are very similar in their nature, so
> changing only one of them might seem inconsistent.
>
> Personally I don't see much use in allowing expressions in isset().
> People being confused by empty(trim($_GET['foo'])) not working is
> quite common, but I've never heard of somebody trying to use isset()
> on a function call. The name already makes clear that it's intended
> for use on variables.


albeit I'm not laruence, but I also supported the idea to keep consistency
across the allowed params of empty and isset.
here is my reasoning:
- both isset and empty are language constructs, which many people use
almost interchangeability, changing one of them in a way that the same
expression works with one of them, but blows up with a parse error seems
wrong to me.
- maybe you think that isset doesn't really make sense with expressions,
but don't forget that this patch would also allow constants to be used with
empty/isset, and imo isset(some_constant); would be useful and maybe more
straightforward for the people new to the language.

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Hi,

On Tue, May 1, 2012 at 18:43, Ferenc Kovacs <[email protected]> wrote:
>
> albeit I'm not laruence, but I also supported the idea to keep consistency
> across the allowed params of empty and isset.
> here is my reasoning:
> - both isset and empty are language constructs, which many people use
> almost interchangeability, changing one of them in a way that the same
> expression works with one of them, but blows up with a parse error seems
> wrong to me.
> - maybe you think that isset doesn't really make sense with expressions,
> but don't forget that this patch would also allow constants to be used with
> empty/isset, and imo isset(some_constant); would be useful and maybe more
> straightforward for the people new to the language.


So isset(UNDEFINEDCONSTANT) will be isset("UNDEFINEDCONSTANT") which will/should
1) yield a notice, which is unnexpected for isset
2) return true, which is also unexpected.

I don't see much point in that.

Best regards,

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2012/5/1 Ferenc Kovacs <[email protected]>:
> On Mon, Apr 30, 2012 at 2:39 PM, Nikita Popov <[email protected]>wrote:
> - both isset and empty are language constructs, which many people use
> almost interchangeability, changing one of them in a way that the same
> expression works with one of them, but blows up with a parse error seems
> wrong to me.

I wish that more wrong usages could blow up with parse errors way
before waiting for the incorrect line to be run.
While there is some valid use cases for empty() I see none for
isset(), it must remain a targeted and specific construct IMHO.

> - maybe you think that isset doesn't really make sense with expressions,

exact :)

> but don't forget that this patch would also allow constants to be used with
> empty/isset.

That is not a very good think IMO.

For the same reason: this patch would also allow writing: empty( false
) or empty( null ) which are both clueless.
The fact that this patch would now allow syntactically doubtful things
doesn't mean they should be encouraged nor propagated to isset().

Cheers,
Patrick

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On Tue, May 1, 2012 at 7:24 PM, Patrick ALLAERT <[email protected]>wrote:

> 2012/5/1 Ferenc Kovacs <[email protected]>:
> > On Mon, Apr 30, 2012 at 2:39 PM, Nikita Popov <[email protected]
> >wrote:
> > - both isset and empty are language constructs, which many people use
> > almost interchangeability, changing one of them in a way that the same
> > expression works with one of them, but blows up with a parse error seems
> > wrong to me.
>
> I wish that more wrong usages could blow up with parse errors way
> before waiting for the incorrect line to be run.
>

One could argue that then you should pick a compiled language.


> While there is some valid use cases for empty() I see none for
> isset(), it must remain a targeted and specific construct IMHO.
>

I agree that there is less valid use-cases, but I feel that keeping the two
method consistent about this is more important.


>
> > - maybe you think that isset doesn't really make sense with expressions,
>
> exact :)
>
> > but don't forget that this patch would also allow constants to be used
> with
> > empty/isset.
>
> That is not a very good think IMO.
>
> For the same reason: this patch would also allow writing: empty( false
> ) or empty( null ) which are both clueless.
>

how is that different than for example writing is_null(null) ?


> The fact that this patch would now allow syntactically doubtful things
> doesn't mean they should be encouraged nor propagated to isset().
>

we are already have that all over the place, I don't think that this
particular patch will change anything about that.
could you elaborate on this part a little bit?
I mean you can write "stupid" code right now ($null=null;isset($null);
instead of isset(null);), I can't see how would this patch worsen the
situation. If anything, the silly code could be understood easier, as you
wouldn't need to debug the value of the $null variable passed in.
So I think that
1, we already too late to prevent that kind of code
2. even if we could, I don't think that the currently discussed patch would
really encourage that kind of code
3, there are/could be valid use-cases for isset
4, isset and empty should work the same way in regards of the argument
parsing.

ofc. this is only my opinion, if I am the minority here, then it is fine
too, I just wanted to explain what was the reasoning behind that discussion..

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>
>
> So isset(UNDEFINEDCONSTANT) will be isset("UNDEFINEDCONSTANT") which
> will/should
> 1) yield a notice, which is unnexpected for isset
> 2) return true, which is also unexpected.
>
> I don't see much point in that.
>
>
yep, and if we allow expressions then it is the expected behavior, but you
are right that this is will change the current standard that isset/empty
can't raise a notice.
but this isn't specific to isset, empty will also follow the same pattern.

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Sent from my iPhone

在 2012-5-2,3:52,Ferenc Kovacs <[email protected]> 写道:

>>
>>
>> So isset(UNDEFINEDCONSTANT) will be isset("UNDEFINEDCONSTANT") which
>> will/should
>> 1) yield a notice, which is unnexpected for isset
>> 2) return true, which is also unexpected.
>>
>> I don't see much point in that.
>>
>>
> yep, and if we allow expressions then it is the expected behavior, but you
> are right that this is will change the current standard that isset/empty
> can't raise a notice.
> but this isn't specific to isset, empty will also follow the same pattern..
>
This is really a issue .

Thanks
> --
> Ferenc Kovács
> @Tyr43l - http://tyrael.hu

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On Mon, Apr 30, 2012 at 3:50 PM, Patrick ALLAERT <[email protected]> wrote:
> Hi,
>
> 2012/4/12 Nikita Popov <[email protected]>:
>> PS: I added isset() too, to address the consistency concerns mentioned on IRC.
>
> I would have voted +1 if it didn't contain the isset() change. None of
> the examples used in the isset_with_expr.phpt test seems logic to me.
Hi:
isset and empty are generally think as a pair, and the both even
share one ZEND_OP: ZEND_ISSET_ISEMPTY_VAR

so I think if you want to change empty, you should also change isset.

thanks
>
> Care to explain the consistency concerns here?
>
> Patrick
>
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>



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hi,

On Wed, May 2, 2012 at 10:46 AM, Laruence <[email protected]> wrote:

>    so I think if you want to change empty, you should also change isset.

An expression is not set per se. isset goals, by design, from the very
1st day, is to test the existence of a variable and a variable only.

empty() on the other hand, tests if something is empty, and only if it
is empty. The result of an expression can be empty.

Cheers,
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On Wed, May 2, 2012 at 11:10 AM, Pierre Joye <[email protected]> wrote:

> hi,
>
> On Wed, May 2, 2012 at 10:46 AM, Laruence <[email protected]> wrote:
>
> > so I think if you want to change empty, you should also change isset..
>
> An expression is not set per se. isset goals, by design, from the very
> 1st day, is to test the existence of a variable and a variable only.
>

"Returns TRUE if var exists and has value other than NULL, FALSE otherwise."

$foo=null;
var_dump(isset($foo)); //prints bool(false)


>
> empty() on the other hand, tests if something is empty, and only if it
> is empty. The result of an expression can be empty.
>
>
an expression can also have a value of null.

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hi,

On Wed, May 2, 2012 at 11:36 AM, Ferenc Kovacs <[email protected]mail.com> wrote:

> $foo=null;
> var_dump(isset($foo)); //prints bool(false)

No offset meant, but it is totally expected and well known, and as far
as I remember documented too. Assigning NULL to a variable unsets it
(so to say).

>> empty() on the other hand, tests if something is empty, and only if it
>> is empty. The result of an expression can be empty.
>>
>
> an expression can also have a value of null.

And NULL is empty. No issue here.

Cheers,
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On Wed, May 2, 2012 at 11:43 AM, Pierre Joye <[email protected]> wrote:
> hi,
>
> On Wed, May 2, 2012 at 11:36 AM, Ferenc Kovacs <[email protected]> wrote:
>
>> $foo=null;
>> var_dump(isset($foo)); //prints bool(false)
>
> No offset meant,

lapsus :) s,offset,offense,



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Pierre,

On Wed, May 2, 2012 at 5:43 AM, Pierre Joye <[email protected]> wrote:
> hi,
>
> On Wed, May 2, 2012 at 11:36 AM, Ferenc Kovacs <[email protected]> wrote:
>
>> $foo=null;
>> var_dump(isset($foo)); //prints bool(false)
>
> No offset meant, but it is totally expected and well known, and as far
> as I remember documented too. Assigning NULL to a variable unsets it
> (so to say).

Well, except that it doesn't unset it. It only fails isset(). The
symbol still exists in the symbol table, and the zval is still
allocated. That's one reason that isset() can return false, and
array_key_exists() will return true. But right now there's no way to
check if a symbol exists since isset returns falls for a null value in
a symbol (and there's no other way to check it)...

Not saying it should change, just that it's a corner case that's not
accounted for in the API...

I voted for the ability to use an expression for isset() as well,
since I agree with Ferenc, it's a matter of consistency. Sure, the
use-case for isset() is definitely weaker than for empty(), but at the
same token they are definitely related...

Anthony

>>> empty() on the other hand, tests if something is empty, and only if it
>>> is empty. The result of an expression can be empty.
>>>
>>
>> an expression can also have a value of null.
>
> And NULL is empty. No issue here.
>
> Cheers,
> --
> Pierre
>
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>
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On Wed, May 2, 2012 at 11:43 AM, Pierre Joye <[email protected]> wrote:

> hi,
>
> On Wed, May 2, 2012 at 11:36 AM, Ferenc Kovacs <[email protected]> wrote:
>
> > $foo=null;
> > var_dump(isset($foo)); //prints bool(false)
>
> No offset meant, but it is totally expected and well known, and as far
> as I remember documented too. Assigning NULL to a variable unsets it
> (so to say).
>
>
sure, as I quoted the documentation here.
I just wanted to emphasize, that isset not only checks if a variable is set
or not, but also checks the value of the variable, which makes your
argument ("An expression is not set per se. isset goals, by design, from
the very1st day, is to test the existence of a variable and a variable
only.") much weaker.



> >> empty() on the other hand, tests if something is empty, and only if it
> >> is empty. The result of an expression can be empty.
> >>
> >
> > an expression can also have a value of null.
>
> And NULL is empty. No issue here.
>

yeah, but that wasn't my point, I was saying that an expression can also
have a value of null, which can be checked by isset, so empty and isset
isn't any different in that regard for expressions.

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hi Anthony,

On Wed, May 2, 2012 at 1:37 PM, Anthony Ferrara <[email protected]> wrote:

> I voted for the ability to use an expression for isset() as well,
> since I agree with Ferenc, it's a matter of consistency.  Sure, the
> use-case for isset() is definitely weaker than for empty(),

No, it is not about consistency but goals and meaning. An expression
is not set or unset. Anyway, that's not something we can argue about
forever :-).

Cheers,
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Anthony Ferrara wrote:
> I voted for the ability to use an expression for isset() as well,
> since I agree with Ferenc, it's a matter of consistency. Sure, the
> use-case for isset() is definitely weaker than for empty(), but at the
> same token they are definitely related...

I just can't help feeling that it is the wrong use of both. If the function is
returning a value, then it's returning a value that needs to be used somewhere
so the work flow handles that. If the function returns nothing instead that just
seems wrong and needs to be handled better. I'm used to getting back 'false' if
the function failed and just check for that so why would there be any logical
reason for using isset or empty to check a function return?

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2012/5/3 Lester Caine <[email protected]>:
> Anthony Ferrara wrote:
>>
>> I voted for the ability to use an expression for isset() as well,
>> since I agree with Ferenc, it's a matter of consistency.  Sure, the
>> use-case for isset() is definitely weaker than for empty(), but at the
>> same token they are definitely related...
>
>
> I just can't help feeling that it is the wrong use of both. If the function
> is returning a value, then it's returning a value that needs to be used
> somewhere so the work flow handles that. If the function returns nothing
> instead that just seems wrong and needs to be handled better. I'm used to
> getting back 'false' if the function failed and just check for that so why
> would there be any logical reason for using isset or empty to check a
> function return?

Use case:

// Function definition:
function getFriends()
{
// SQL SELECT or Fetching from XML or Fetching from LDAP or ...
return $resultsAsArray;
}

// Looping on results:
foreach ( getFriends() as $friend )
{
echo $friend["name"], "\n";
}

// Case where the results are actually not iterated:
$amIAssocial = empty( getFriends() );

1. It it not wrong to return "nothing", like empty sets (empty
arrays), it is a valid case.
2. Returning "false" in the case there is no "results" would be a bad
idea: not only you would have to put a condition in the function
definition, but you would also require all iterations (e.g. foreach)
to be encapsulated in a condition statement to prevent looping on
"false".

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>> I just can't help feeling that it is the wrong use of both. If the function
>> is returning a value, then it's returning a value that needs to be used
>> somewhere so the work flow handles that. If the function returns nothing
>> instead that just seems wrong and needs to be handled better. I'm used to
>> getting back 'false' if the function failed and just check for that so why
>> would there be any logical reason for using isset or empty to check a
>> function return?
>
> Use case:
>
> // Function definition:
> function getFriends()
> {
>    // SQL SELECT or Fetching from XML or Fetching from LDAP or ....
>    return $resultsAsArray;
> }
>
> // Looping on results:
> foreach ( getFriends() as $friend )
> {
>    echo $friend["name"], "\n";
> }
>
> // Case where the results are actually not iterated:
> $amIAssocial = empty( getFriends() );

This is the exact same thing:
$amIAssocial = !getFriends();


Earlier, I sent this to Lester only:
Most people don't realize that an empty array is already falsy so they
feel the need to use empty. That is the only use-case the RFC gives
for making this change. From the RFC: "For example if func() is
expected to return an array, it feels more natural to verify it's
emptiness using empty() instead of !."
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Patrick ALLAERT wrote:
> 2012/5/3 Lester Caine<[email protected]>:
>> Anthony Ferrara wrote:
>>>
>>> I voted for the ability to use an expression for isset() as well,
>>> since I agree with Ferenc, it's a matter of consistency. Sure, the
>>> use-case for isset() is definitely weaker than for empty(), but at the
>>> same token they are definitely related...
>>
>>
>> I just can't help feeling that it is the wrong use of both. If the function
>> is returning a value, then it's returning a value that needs to be used
>> somewhere so the work flow handles that. If the function returns nothing
>> instead that just seems wrong and needs to be handled better. I'm used to
>> getting back 'false' if the function failed and just check for that so why
>> would there be any logical reason for using isset or empty to check a
>> function return?
>
> Use case:
>
> // Function definition:
> function getFriends()
> {
> // SQL SELECT or Fetching from XML or Fetching from LDAP or ...
> return $resultsAsArray;
> }
>
> // Looping on results:
> foreach ( getFriends() as $friend )
> {
> echo $friend["name"], "\n";
> }
>
> // Case where the results are actually not iterated:
> $amIAssocial = empty( getFriends() );
>
> 1. It it not wrong to return "nothing", like empty sets (empty
> arrays), it is a valid case.
> 2. Returning "false" in the case there is no "results" would be a bad
> idea: not only you would have to put a condition in the function
> definition, but you would also require all iterations (e.g. foreach)
> to be encapsulated in a condition statement to prevent looping on
> "false".

OK I'm just so used to
if( $rs = $this->mDb->query( $query, $bindVars ) ) {
while( $row = $rs->fetchRow() ) {
}
}

So I can't see where 'empty( $rs->fetchRow() )' would fit into the work flow ...

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On Wed, May 2, 2012 4:43 am, Pierre Joye wrote:
>>> empty() on the other hand, tests if something is empty, and only if
>>> it
>>> is empty. The result of an expression can be empty.
>>>
>>
>> an expression can also have a value of null.
>
> And NULL is empty. No issue here.

Expressions can also return "", 0, 0.0, "0", array()

You really think those should all be empty?

Or you want different behavior for expressions vs variables. I'm
assuming virtually everybody would agree THAT is unacceptable...

Or are the rules for what is or isn't empty going to also change. Again.

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On Fri, May 4, 2012 at 11:48 AM, Richard Lynch <[email protected]> wrote:

> On Wed, May 2, 2012 4:43 am, Pierre Joye wrote:
> >>> empty() on the other hand, tests if something is empty, and only if
> >>> it
> >>> is empty. The result of an expression can be empty.
> >>>
> >>
> >> an expression can also have a value of null.
> >
> > And NULL is empty. No issue here.
>
> Expressions can also return "", 0, 0.0, "0", array()
>
> You really think those should all be empty?
>

Unless I'm missing something here, aren't all those things already
considered to be empty?? Here's what the PHP man page for empty() says:

The following things are considered to be empty:

- *""* (an empty string)
- *0* (0 as an integer)
- *0.0* (0 as a float)
- *"0"* (0 as a string)
- *NULL*
- *FALSE*
- *array()* (an empty array)
- *var $var;* (a variable declared, but without a value in a class)


If that's the way it already behaves, then why would keeping it that way
even be an issue? If an expression returns any of those things, it's empty.

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? The answer seems to
be yes as far as I can tell. And if that is the case, then what value is
there in allowing it if the return value is always the same no matter what?

--Kris
>
>
> 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.
and as I mentioned expressions can return null, so it isn't true that any
expression given to isset would always result in true.
but I think we were talked this over already, so not much point repeating
the same arguments over and over again.

to summarize, the following cons were brought up against allowing
expressions for isset :


- if you pass an undefined constant to isset, you will get unexpected
result as isset will raise a notice and can return unexpected result as the
constant is casted to string before being passed to isset(btw. this is how
expressions work everywhere else, so it isn't a real surprise, but it is a
change to the current behavior).
- this is a valid concern, but the same problem applies to empty too,
so it is a general problem with the current patch/rfc. I think
it would be
nice mentioning this in the rfc, as this could/will cause a few
wtf moments
for some people.
- isset(CONST) could be seen as defined("CONST") but they are returning
different results if CONS is defined with NULL or undefined.
- this is a valid concern, and there is no good solution, for
isset(CONST) we either go cosistent with isset or declared, but can't do
both at the same time.
- semantically empty can make sense for expressions, isset doesn't:
- yep, the only thing that makes this a little less clear/obvious is
the fact that isset in php also checks for value, not only the
"existence"
of the variable.
- following the previous point, there are much more fluent use-cases for
empty(expression) than for isset(expression)
- this is true, for null check you should use comparing the value,
for other cases empty could be much more useful, only the isset(CONST)
could be useful, but I mentioned the problems with that above.

after discussing this and thinking it over a few times, I decided that I
will drop my case about supporting both empty and isset.
I think that keeping the argument handling for isset and empty in sync
doesn't worth the possible gotchas.
and I now a little less sure about suporting this change for empty(), given
how much do we emphasized over the years that empty won't trigger any
warning about the non-existent variables.

--
Ferenc Kovács
@Tyr43l - http://tyrael.hu
On Fri, May 4, 2012 at 1:27 PM, Ferenc Kovacs <[email protected]> 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
>
>
> 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.
>
>
then maybe you should open a separate rfc and thread for that.
btw. $foo = null; doesn't equals/aliases unset($foo); only isset() written
in a way so that it checks the existence of the variable AND if it exists
then checks that it's value isn't null.
maybe this isn't nice for a newcommer to the language, but it is how isset
works for a pretty long time now, and changing it would be a major BC break..
not impossible, but that would definitively deserve a separate RFC and
discussion.

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@Tyr43l - http://tyrael.hu
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