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To: Mike Schinkel <mike@newclarity.net>
CC: Internals <internals@lists.php.net>
Thread-Topic: [PHP-DEV] RFC idea: Block scoped variables with "let $x =  expr"
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Date: Sun, 15 Mar 2020 18:53:58 +0000
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Subject: Re: [PHP-DEV] RFC idea: Block scoped variables with "let $x =  expr"
From: tysonandre775@hotmail.com (tyson andre)

Hi Mike,=0A=
=0A=
> What I would rather see are new features in PHP that encourage developer=
=0A=
> to break functionality into shorter and simpler functions and methods, an=
d to minimize nesting.=0A=
=0A=
I would also like to see shorter functions in general, but:=0A=
=0A=
- Other developers may prefer long functions/scripts despite my preferences=
,=0A=
=A0 but their code would still benefit from readability by having block-sco=
ped variables enforced by the compiler=0A=
- Some problem domains are complex (e.g. business logic) and require a lot =
of variables,=0A=
=A0 leading to long functions/scripts, and trying to split them up may be e=
rror-prone=0A=
=A0 or cause awkward divisions of functionality.=0A=
- Even in short functions of a few dozen lines, it may be useful to know if=
 reused variables such as=0A=
=A0 `$i` are definitely scoped to a loop, when reviewing code.=0A=
=0A=
> There is also an issue with block scoping that is reasonably well-known=
=0A=
> among the GoLang community called variable shadowing=0A=
> and that is a developer seeing a variable in block scoping=0A=
> and thinking they are accessing or assigning the function-scoped variable=
.=0A=
=0A=
Variable shadowing is also an issue in JavaScript.=0A=
While JavaScript and GoLang don't allow introspection of the variable scope=
=0A=
(as far as I know, not sure about reflection),=0A=
PHP does allow dynamic access by name ($$var, `get_defined_variables()['var=
']` in a require()d file, XDebug),=0A=
and any proposal for block scoping in PHP will need to account for that som=
ehow.=0A=
=0A=
- Aside: Personally, I set up linting for golang projects to forbid shadowi=
ng.=0A=
=0A=
My best plan for dealing with variable shadowing in PHP was to forbid it en=
tirely,=0A=
which I mentioned examples of in the proposal.=0A=
=0A=
> {=0A=
> =A0 =A0let $outer =3D 1;=0A=
> =A0 =A0{=0A=
> =A0 =A0 =A0 =A0let $outer =3D 2; =A0// E_COMPILE_ERROR to declare in a di=
fferent (shadowed) scope, can only reassign=0A=
> =A0 =A0 =A0 =A0$outer =3D 3; =A0 // this is allowed=0A=
> =A0 =A0 }=0A=
> }=0A=
=0A=
> P.S. If you really need block scope within a long function or method you =
can already create a closure and call it in the same expression:=0A=
=0A=
I'm aware of this and have used it (e.g. to avoid modifying the global scop=
e in large projects),=0A=
but avoid it in functions due to the awkward syntax and the performance ove=
rhead of function calls.=0A=
I'd generally just use a different variable name.=0A=
=0A=
- Tyson=