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To: Manuel Canga <php@manuelcanga.dev>, Internals <internals@lists.php.net>
Thread-Topic: [PHP-DEV] [RFC] Import of variables
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Date: Sun, 9 Aug 2020 14:41:44 +0000
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Subject: Re: [PHP-DEV] [RFC] Import of variables
From: tysonandre775@hotmail.com (tyson andre)

Hi Internals,=0A=
=0A=
> This functionality would allow to create a new=A0 'use vars' keyword in o=
rder to can use( or cannot use )=A0 global variables in local scope( of cur=
rent file ).=0A=
=0A=
To be clear: The variables in the top-level scope depend on what has requir=
e()d/include()d a file.=0A=
The top-level scope starts off as being global, but if a file is required f=
rom within a function/method/closure (e.g. the autoloader closure), then th=
e top-level scope in the require()'d file uses variables (e.g. $this) from =
whatever context called require().=0A=
=0A=
It may be possible to use a declare syntax, e.g. declare(used_variables=3D'=
all') for `'all'`, `null`, `['var1', 'var2']`, etc.=0A=
- Otherwise, you face the issue of where `use vars` should be allowed, what=
 happens if there's a statement before `use vars`, etc.=0A=
=0A=
I can see this as having some use cases, such as in configuration files or =
files used for bootstrapping.=0A=
For example,=0A=
=0A=
```=0A=
<?php=0A=
declare(used_variables=3Dnull);=0A=
=0A=
$api_base =3D IS_PRODUCTION ? 'https://example.com/api/' : 'http://localhos=
t/api';=0A=
do_stuff();=0A=
=0A=
return [=0A=
    // long config array=0A=
    'url_new' =3D> "$api_base/new",=0A=
    'url_all' =3D> "$api_base/all",=0A=
];=0A=
```=0A=
=0A=
This feature (ignoring the question of syntax) would ensure that people rea=
ding the file knew that $api_base was not modified by other files=0A=
and that other files did not read local variables created within a configur=
ation/bootstrapping file in unexpected ways,=0A=
which is a fairly common issue in some web apps I've worked on.=0A=
Opcache would also do a better job at optimizing code if it knew which vari=
ables in a top-level scope couldn't be modified.=0A=
=0A=
That being said, there's been opposition to extensions to the language that=
 add functionality that can be implemented in other ways, as in Rowan's com=
ment,=0A=
but peoples opinions depend on the specifics of the proposal=0A=
(e.g. `match` was added and was more performant than chained conditionals o=
r switch).=0A=
=0A=
As Rowan said, there are ways to reimplement this:=0A=
- Wrapping the config file or bootstrapping file in a closure, global funct=
ion, or class method=0A=
- `function safe_require_once(string $path, $vars =3D []) { extract($vars);=
 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, thou=
gh.=0A=
=0A=
Regards,=0A=
- Tyson=