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Date: Tue, 21 Apr 2026 19:52:06 +0200
To: php internals <internals@lists.php.net>
Subject: [PHP-DEV] [RFC] Partial Function Application: Handling of Optional Parameters
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From: tim@bastelstu.be (=?UTF-8?Q?Tim_D=C3=BCsterhus?=)

Hi

as part of the design for a “PFA for $this” RFC, Arnaud and I came 
across one issue in the original design of PFA that makes it hard to do 
the “PFA for $this” follow-up in a way that does not violate user 
expectations. Specifically the handling of “optional parameters”. With 
the support of Larry as one of the original authors of the PFA RFC, we 
would like to propose an amendment to the PFA RFC that is unlikely to 
affect real-world use-cases, but that will enable these follow-ups and 
that will result in a more predictable behavior overall.

Please find all details in the RFC at: 
https://wiki.php.net/rfc/partial_function_application_optional_placeholder

Unless significant discussion happens, I expect the RFC to go to vote in 
2 weeks, so that it can be incorporated in the PFA implementation right 
away.

Best regards
Tim Düsterhus