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Date: Tue, 11 Nov 2025 22:43:39 +0000
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Subject: Re: [PHP-DEV] [RFC][Discussion] use construct (Block Scoping)
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

On 11/11/2025 21:12, Tim Düsterhus wrote:

> That's fair. I'll look into adding more explicit comparisons to the 
> RFC together with Seifeddine. My short answer here would be that 
> JavaScript already had explicit scoping by means of `var` and thus 
> folks are already used to needing to declare variables. Moving to 
> `let` is just a smaller incremental change. This is different from PHP 
> where all variables exist implicitly, which also means that semantics 
> from other languages need to be adapted.


Technically, JavaScript variables don't have to be declared either; the 
difference is that they are global by default, and since function-scope 
is generally more useful, people are indeed very familiar with "var".


PHP does have optional keywords that declare a variable with specific 
scope, just much less frequently used: "global" and "static". Regarding 
the discussion on shadowing vs hoisting:

- Both "global" and "static" can shadow local variables, and indeed each 
other: https://3v4l.org/vPr2A
- Since the shadowing lasts until the end of the function, a shadowed 
local variable is never re-instated, and will be de-allocated if it was 
the only reference: https://3v4l.org/VBVkX
- Somewhat unusually, they do this as run-time statements, so you can 
*conditionally* shadow variables: https://3v4l.org/fK9VJ

Whether these are *good* semantics to copy for a block-scoped variable, 
I'm not sure; but they are existing PHP semantics for a very similar 
situation.



>>  I'm not aware of any language that requires a specific kind of block 
>> in order to introduce a new scope, but that doesn't mean it's a bad 
>> idea. The approaches I am aware of are:
>
> The closest comparison to “specific kind of block” might perhaps be 
> older versions of C which require all variables to be declared - and 
> for them to be declared at the top of the scope without any logic 
> running in-between.


The big difference is the need for an extra level of indent (or, at 
least, an extra pair of braces, which most people will probably assume 
needs an extra level of indent). More often than not, there is an 
existing block you want to scope to - a particular loop, or a 
conditional branch, etc.

I do see the advantage of forcing them to the start, though. Languages 
in the Pascal family might be another comparison to explore - variables 
are all declared in a separate block at the top of a function. Off-hand, 
I'm not sure if any allow an arbitrary nested block just to introduce 
additional variables.


Regards,

-- 
Rowan Tommins
[IMSoP]