Newsgroups: php.internals
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Xref: news.php.net php.internals:111407
Date: Sun, 09 Aug 2020 23:57:26 +0200
To: "tyson andre" <tysonandre775@hotmail.com>
Cc: "Internals" <internals@lists.php.net>
Message-ID: <173d5399f3c.e6304d5b580764.6781921355672822606@manuelcanga.dev>
In-Reply-To: <DM6PR07MB66189348DC25742658121507F9470@DM6PR07MB6618.namprd07.prod.outlook.com>
References: <173d2736435.eeebc066559719.6668730031195302987@manuelcanga.dev> <DM6PR07MB66189348DC25742658121507F9470@DM6PR07MB6618.namprd07.prod.outlook.com>
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Subject: Re: [PHP-DEV] [RFC] Import of variables
From: php@manuelcanga.dev (Manuel Canga)

Hi, Tyson,  Thanks.=20


 ---- En dom, 09 ago 2020 16:41:44 +0200 tyson andre <tysonandre775@hotmail=
.com> escribi=C3=B3 ----
 > Hi Internals,
 >=20
 > To be clear: The variables in the top-level scope depend on what has req=
uire()d/include()d a file.
 > The top-level scope starts off as being global, but if a file is require=
d from within a function/method/closure (e.g. the autoloader closure), then=
 the top-level scope in the require()'d file uses variables (e.g. $this) fr=
om whatever context called require().

My idea was using 'use vars' not only with global vars but also with vars i=
n context.

 > It may be possible to use a declare syntax, e.g. declare(used_variables=
=3D'all') for `'all'`, `null`, `['var1', 'var2']`, etc.
 > - Otherwise, you face the issue of where `use vars` should be allowed, w=
hat happens if there's a statement before `use vars`, etc.

Good point, I don't think about that.=20

 > I can see this as having some use cases, such as in configuration files =
or files used for bootstrapping.
 > For example,
 >=20
 > ```
 > <?php
 > declare(used_variables=3Dnull);
 >=20
 > $api_base =3D IS_PRODUCTION ? 'https://example.com/api/' : 'http://local=
host/api';
 > do_stuff();
 >=20
 > return [
 >     // long config array
 >     'url_new' =3D> "$api_base/new",
 >     'url_all' =3D> "$api_base/all",
 > ];
 > ```
 >=20
 > This feature (ignoring the question of syntax) would ensure that people =
reading the file knew that $api_base was not modified by other files
 > and that other files did not read local variables created within a confi=
guration/bootstrapping file in unexpected ways,
 > which is a fairly common issue in some web apps I've worked on.
 > Opcache would also do a better job at optimizing code if it knew which v=
ariables in a top-level scope couldn't be modified.
 >=20
 > That being said, there's been opposition to extensions to the language t=
hat add functionality that can be implemented in other ways, as in Rowan's =
comment,
 > but peoples opinions depend on the specifics of the proposal
 > (e.g. `match` was added and was more performant than chained conditional=
s or switch).
 >=20
 > As Rowan said, there are ways to reimplement this:
 > - Wrapping the config file or bootstrapping file in a closure, global fu=
nction, or class method
 > - `function safe_require_once(string $path, $vars =3D []) { extract($var=
s); require($path); }` from the caller, to limit what variables are passed =
in. IDEs/tooling would be worse at telling you if a file name had a typo, t=
hough.

I think in views system( of some frameworks )  or CMS like WordPress. In Wo=
rdPress, for example, I can do something like this:

## index.php

```
foreach($posts as $post ) {
   $post =3D 'foo';
}
```

index.php is loaded from CMS. $post is a global variable used in WordPress =
core. So that, I am crashing WordPress. However, with:

```
use vars none;

foreach($posts as $post ) {
   $post =3D 'foo';
}
```

I don't crash my WordPress or any external plugin which can use global vars=
. My file now is a container( black box ) where my code is isolated.

Regards