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Date: Mon, 30 Mar 2026 08:37:19 +0100
To: internals@lists.php.net
Subject: Re: [PHP-DEV] RFC proposal: Invokable interface
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From: imsop.php@rwec.co.uk ("Rowan Tommins [IMSoP]")

On 30 March 2026 01:32:24 BST, Osama Aldemeery <aldemeery@gmail=2Ecom> wrot=
e:

>The only difference is that __toString() has a fixed signature, so
>Stringable can enforce it through a normal interface declaration=2E
>__invoke() doesn't
>have a fixed signature, so Invokable uses an enforcement handler instead=
=2E
>Different mechanism, same contract=2E The difference is caused by the
>variable signature, not by any fundamental difference in what the interfa=
ce
>represents=2E

I think that is a very fundamental difference=2E

Given $foo instanceof Stringable, the user knows they can write (string)$f=
oo and the object will do something - that's already a pretty weak contract=
, in my eyes, but it is a contract=2E

Given $foo instanceof Invokable, the user knows even less=2E They know the=
y can invoke the object somehow, but there's a fair chance that $foo() will=
 fail because of mandatory parameters=2E

Can you give an example where this very loose contract would be useful?

Regards,

Rowan Tommins
[IMSoP]