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Date: Wed, 2 Sep 2015 10:06:05 +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 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, I would have simply used isset() without =
thinking (this being a problem if the variable was set to NULL).

Whereas, if I was told to check if the variable was NULL, I would do an =
"$a =3D=3D=3D NULL" or is_null().

It might just be due to the functions name length or usage, while =
wanting to avoid undefined variable notices:

<?php

  $search =3D (isset($_GET['q']) ? $_GET['q'] : '');

  $search =3D (array_key_exists('q', $_GET) ? $_GET['q'] : '');

?>

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).

And the second one does not really check for the existence of $_GET, =
which in this case is probably ok.

Craig






On 1 Sep 2015, at 19:17, Rowan Collins <rowan.collins@gmail.com> wrote:

> On 01/09/2015 10:29, Craig Francis wrote:
>> Personally I still like the idea of an exists(), because I feel that =
is how many programmers treat and use the isset() function - simply =
because they do use NULL as a valid value, and either haven't read the =
manual, or forget the exception that is mentioned on line 1 (something =
I've done a couple of times).
>=20
> I'm still not sure how exists() would be anything other than an alias =
for array_key_exists().
>=20
> Once again, this is NOT about "using NULL as a valid value"; it's =
about "using a variable's NON-EXISTENCE as a valid state". I think that =
is the fundamental mistake people make - they think the "quirk" is that =
isset() returns false for a null value, when that is the most rational =
part of it. The "quirk" is that you don't get a warning when passing a =
completely undefined variable to isset().
>=20
> Obviously, that's not something that's likely to change, but as you =
say, what we are really testing is "the value pointed at by some =
identifier". In an array, that identifier can be dynamic, but in plain =
variable scope, that identifier is something you the programmer have =
defined long before the program executed, so its existence is never in =
question.
>=20
> Looked at that way, the handling of unitialised variables is just a =
side-effect of the handling of NULLs, since all unitialised variables =
have a default/implicit value of NULL.
>=20
> Regards,
>=20
> --=20
> Rowan Collins
> [IMSoP]
>=20
>=20
> --=20
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>=20