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Date: Mon, 7 Sep 2015 14:11:05 +0100
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To: Rowan Collins <rowan.collins@gmail.com>
Subject: Re: [PHP-DEV] PHP 7.1 - Address PHPSadness #28?
From: craig@craigfrancis.co.uk (Craig Francis)


On 2 Sep 2015, at 13:31, Rowan Collins <rowan.collins@gmail.com> wrote:

> 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.




Maybe... personally I don't see why anyone would be performing =
operations such as:

   exists($foo['bar'] + 1)

In the same way that `isset($a + 1)` results in a parse error.

But then again, I don't think it's a quirk that "you don't get a warning =
when passing a completely undefined variable to isset()", as I don't see =
isset() as a normal function.

If you do treat is as a normal function, you might as well be using =
is_null() or "=3D=3D=3D NULL".

For example, I think its quite common for MVC style frameworks to check =
if a variable exists (with isset) in a View (e.g. checking if a =
paginator exists after printing the table of results).

With the `exists($foo['bar']['baz'])` example, I just see that as a =
simple: if $foo exists, and contains the key 'bar', and contains the key =
'baz' (no need to check values).

Like isset() I see exists() as a special function that isn't passing a =
variable in, but PHP doing some analysis of the thing in the brackets.

Craig






On 2 Sep 2015, at 13:31, Rowan Collins <rowan.collins@gmail.com> wrote:

> Craig Francis wrote on 02/09/2015 10:06:
>> On 1 Sep 2015, at 19:17, Rowan Collins <rowan.collins@gmail.com> =
wrote:
>>=20
>>> I'm still not sure how exists() would be anything other than an =
alias for array_key_exists().
>>=20
>> I think that is the case as well (ish).
>>=20
>> 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.
>>=20
>> Before last week, if someone asked me to write some code to see if a =
variable (or key) exists,
>=20
> 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:
>=20
>=20
>>  I would have simply used isset() without thinking (this being a =
problem if the variable was set to NULL).
>=20
> 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.
>=20
> 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
>=20
>=20
>> The second one does also represent the variable in a different way =
(grep for "$_GET['q']", where it only appears 3 times in that code).
>=20
> This is a more reasonable point, and I was pondering whether it would =
be possible to allow a more natural syntax.
>=20
> It would probably require a lot of "magic" in the engine, though, =
because it would have to parse exists($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).
>=20
>=20
>> And the second one does not really check for the existence of $_GET, =
which in this case is probably ok.
>=20
> I'm not really sure what you mean by this.
>=20
>=20
> 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.
>=20
> Regards,
> --=20
> Rowan Collins
> [IMSoP]