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Subject: Re: [PHP-DEV] [RFC][Discussion] use construct (Block Scoping)
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From: larry@garfieldtech.com ("Larry Garfield")

On Thu, Dec 11, 2025, at 4:21 PM, Rowan Tommins [IMSoP] wrote:


>> Being able to declare variables with =E2=80=9Cif=E2=80=9D lifetime th=
at I can also=20
>> check is a big part of the benefits of the proposed syntax and=20
>> something I'm missing in other languages.
>>
>> =C2=A0=C2=A0=C2=A0 if (let $user =3D $repository->find(1); $user !=3D=
=3D null) { }
>
> I find this more readable than the proposed version:
>
>
>> =C2=A0 =C2=A0 let ($user =3D $repository->find(1)) if ($user !=3D=3D =
null) { }
>
>
> Skimming down a piece of code, I can spot where code is being run=20
> conditionally without reading the condition itself:
>
> if ............ {
>
> With the proposed syntax, that first glance is:
>
> let ........... {
>
> On closer inspection, it's actually:
>
> let ..... if ..... {
>
>
> Maybe it's also because I've dabbled in Perl, which has post-fix=20
> conditions, so a very similar line would have a very different meaning:
>
> my $foo=3Ddo_bar() if ($baz !=3D 0);
>
> is equivalent to:
>
> my $foo;
> if ($baz !=3D 0) { $foo=3Ddo_bar(); }
>
> Which is also a word order we can use in English, e.g. "hang the wet=20
> clothes inside if it is raining".
>
>
> In terms of making it less of a special case, some languages have a=C2=
=A0","=20
> operator which lets you glue any two expressions together and get the=20
> right-hand result.
>
> In Perl, you can write this:
>
> ```
> my $a =3D 'outer', $b =3D 'whatever';
> if ( my $a=3D'inner', $b =3D=3D 'whatever' ) {
>  =C2=A0 =C2=A0 say $a; // 'inner'
> }
> say $a; // 'outer'
> ```
>
> This gives the desired scope for $a, but the if statement is still jus=
t=20
> accepting a single expression.
>
> JavaScript has the same operator, but apparently doesn't allow "let" i=
n=20
> an expression, so you can write:
>
> if ( a=3D"inner", b=3D=3D"whatever" ) { }
>
> but can't use it to declare a local version of "a".
>
>
> I haven't thought through exactly how to apply that to PHP, but it mig=
ht=20
> give us an option for "both and": a concise and reusable syntax for th=
e=20
> if use case, and a separate syntax for cases like the closure example =
I=20
> gave earlier: https://externals.io/message/129059#129075

The more I think on this, the more I think that the auto-unsetting behav=
ior of a `let` would be useful *only* in combination with some other exi=
sting block, not as its own block.

if (let $x=3Dstuff(); $x < 1) { ... }

for (let $i =3D 0; $i < 10; $i++) { ... }

foreach (let $arr as $k =3D>v) { ... } (applies to both $k and $v)

And so on.  (I'm not sure if it makes sense on a while?  Possibly.)  Exa=
ct syntax above is just spitballing.

But that would allow for the mask/unset logic for variables that have sp=
ecial meaning in existing block constructs, which is generally what you'=
d be interested in.  I don't think there's a huge use case for unsetting=
 arbitrary variables in arbitrary places.  It would also be cleaner than=
 the current pattern of if ($x =3D stuff() && $x < 1) {}, which always f=
elt clunky and "leaks" $x.

If you need some thing more arbitrary and custom than cleaning up an exi=
sting block construct, then the additional setup of a Context Manager is=
 fully justified, and more robust.

--Larry Garfield