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Date: Sun, 25 Jan 2026 12:44:29 -0600
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Subject: Re: [PHP-DEV] [RFC] Pattern Matching
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From: larry@garfieldtech.com ("Larry Garfield")

On Sat, Jan 24, 2026, at 12:25 PM, Tim D=C3=BCsterhus wrote:
> Hi
>
> Am 2026-01-23 20:48, schrieb Larry Garfield:
>> The idea of the second being that, if you want just an identity match=
,=20
>> you can skip adding `is` on just that one arm.
>
> I don't understand what that is trying to say.

With a per-arm keyword, one could do this:

$result =3D match ($somevar) {
    is Foo =3D> 'foo', // This matches against the pattern `Foo`, which =
is a class name.
    Bar =3D> 'bar',     // This matches =3D=3D=3D against the constant `=
Bar`, whose value is whatever.
};

The main reason we cannot just auto-detect whether it's a pattern is the=
 confusion between a class name and constant, since a constant is a lega=
l literal value for an identity match.  With per-arm, you can opt-in to =
pattern matching individually, at the cost of having to remember to repe=
at the keyword on every line.  With per-block, you only have to add the =
keyword once at the cost of not being able to selectively use patterns o=
r identity matching.

Which tradeoff is better is the option question.  (Ilija and I disagree =
on which to go with.)  Or, if someone can suggest a way to allow automat=
ic detection reliably, that would also be most welcome. :-)

--Larry Garfield