Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:125430
Content-Type: text/plain;
	charset=utf-8
Precedence: bulk
Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3776.700.51\))
Subject: Re: [PHP-DEV] Local constants
In-Reply-To: <420bb5cb-5fca-4f2e-8c68-0ca327cd3392@app.fastmail.com>
Date: Wed, 4 Sep 2024 17:11:25 -0400
Cc: internals@lists.php.net
Content-Transfer-Encoding: quoted-printable
Message-ID: <7A98532B-7465-4FC5-B7A9-993E7D430EE1@zort.net>
References: <CAPbW5OMLM=0k_WkL1K556O3+cq06X3iQ7OwgPWyjcUzBJ7opRA@mail.gmail.com>
 <27c3909f-05f4-4256-a447-10e8d8760fff@app.fastmail.com>
 <F9C739E2-2FA3-4CAF-9A9B-CE343F84B461@zort.net>
 <420bb5cb-5fca-4f2e-8c68-0ca327cd3392@app.fastmail.com>
To: Rob Landers <rob@bottled.codes>
From: jbafford@zort.net (John Bafford)


> On Sep 4, 2024, at 16:45, Rob Landers <rob@bottled.codes> wrote:
>=20
> I think, conceptually, this makes sense, but maybe I'm the only one =
who writes
>=20
> $arr =3D doSomething();
> $arr =3D array_map(fn($x) =3D> $x->prop, $arr);
> $arr =3D array_filter($arr, $filterFunc);
>=20
> instead of
>=20
> $arr =3D array_filter(array_map(fn($x) =3D> $x->prop, doSomething()), =
$filterFunc);

IMO, that's a failing of PHP not supporting object syntax (and =
reasonable api) for non-object values. In other languages, I can write =
code such as:

let arr =3D doSomething()
    .map { $0.prop }
    .filter(filterFunc)

Which is more readable than both PHP versions.


> And I feel like having constant variables would result in more of the =
latter, which I feel is more unreadable. Though I do note that my =
opinion of what is readable might be different from other people's.
>=20
> That being said, I would much rather see block-scoped variables than =
local variables via let or var or something:
>=20
> var $aNumber =3D 12;
>=20
> foreach($arr as var $item) {
>   echo $item; // item exists here
> }
>=20
> echo $item; // item doesn't exist here
>=20
> PHP is simply too verbose to really benefit from local constants, but =
would benefit from block-scope far more. For example, with local =
constants, you couldn't write that foreach because that variable exists =
in the scope of the function and can only be defined once.
>=20
> =E2=80=94 Rob

I'd suggest that the foreach could be written with either of let/var to =
both locally scope $item, which would explicitly disallow/allow $item to =
be changed while in the loop.

Another benefit of local constants is preventing accidentally reusing a =
prior variable. For example, if I set a temporary variable to something, =
and then later in the function, reuse that same name for a new temporary =
but don't set the value on all flow paths, then the value from earlier =
in the function leaks through, whereas either using a constant, or a =
second explicit variable definition would have exposed and/or prevented =
the issue.

-John