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Date: Tue, 27 Jan 2026 08:40:17 +0000
To: php internals <internals@lists.php.net>
Subject: Re: [PHP-DEV] [RFC] Pattern Matching
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

On 23 January 2026 19:48:31 GMT, Larry Garfield <larry@garfieldtech=2Ecom> =
wrote:
>
>4=2E The variable pinning syntax=2E  There's been some concerns about it =
being non-obvious, which is valid=2E  The main argument for it is "it's wha=
t Ruby does", which is not the most compelling argument, but it's not inval=
id=2E


As I think I've said before, for the average PHP user, the question isn't =
going to be "what's the syntax for variable pinning?", it's going to be "ho=
w do I tell if this variable is input to or output from the pattern?" In ot=
her words, variable binding and variable pinning syntaxes need to be design=
ed as a pair=2E=20

Take this example from the RFC:

if ($p is Point(z: $z, x: 3, y: $y))

To a PHP programmer who has never seen pattern matching before, that looks=
 like it's testing three properties, not doing some destructuring assignmen=
ts=2E If variable pinning isn't supported, they'll soon learn; but if both =
interpretations are supported with subtly different syntax, I can see it be=
coming a major source of bugs=2E Maybe that's why a lot of languages don't =
support pinning at all?=20

The only way I can think to make this less painful is to have some pair of=
 syntaxes that signals "in" and "out", or "read" and "set", in some way=2E =
For example, this looks rather ugly, and may not even be parseable, but it =
signals the behaviour fairly well without having to read the manual:

if ($p is Point(z: $z=3D, x: 3, y: $y=3D))
if ($p is Point(z: =3D=3D$z, x: 3, y: =3D=3D$y))
if ($p is Point(z: =3D=3D$z, x: 3, y: $y=3D))

Regards,

Rowan Tommins
[IMSoP]