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Date: Wed, 2 Sep 2015 13:31:50 +0100
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Subject: Re: [PHP-DEV] PHP 7.1 - Address PHPSadness #28?
From: rowan.collins@gmail.com (Rowan Collins)

Craig Francis wrote on 02/09/2015 10:06:
> On 1 Sep 2015, at 19:17, Rowan Collins <rowan.collins@gmail.com> wrote:
>
>> I'm still not sure how exists() would be anything other than an alias for array_key_exists().
>
> I think that is the case as well (ish).
>
> But considering that isset() seems to be the function that is used most of the time, I want to consider why that is the case.
>
> Before last week, if someone asked me to write some code to see if a variable (or key) exists,

Again, you insist on drawing a false equivalence to the different 
concepts of variable and array key. This makes the following sentence 
really easy to dismiss:


>   I would have simply used isset() without thinking (this being a problem if the variable was set to NULL).

No, it wouldn't be a problem if a VARIABLE was set to null, because 
there is no practical difference between an unset variable and one set 
to null, so you never need to ask which you have.

It *would* be a problem if you were testing for the existence of an 
array key. There should probably be a prominent link to 
array_key_exists() and property_exists() on the isset() manual page


> The second one does also represent the variable in a different way (grep for "$_GET['q']", where it only appears 3 times in that code).

This is a more reasonable point, and I was pondering whether it would be 
possible to allow a more natural syntax.

It would probably require a lot of "magic" in the engine, though, 
because it would have to parse exists($foo['bar']['baz']) in some 
special way to know that it needed to first find the value of 
$foo['bar'], and then do an existence check for key 'baz', rather than 
just treating the whole thing as an expression to resolve before 
exists() was called. Evaluating things like exists(foo()[ bar() ]) 
correctly might get messy, as would giving a meaningful result or error 
if you wrote exists($foo['bar'] + 1).


> And the second one does not really check for the existence of $_GET, which in this case is probably ok.

I'm not really sure what you mean by this.


In summary, I don't think any language change is needed here, but 
documentation needs to be improved. I will have a go at drafting a new 
intro for the isset() page when/if I get time.

Regards,
-- 
Rowan Collins
[IMSoP]