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Date: Mon, 2 Sep 2019 16:03:08 +0200
To: PHP internals <internals@lists.php.net>
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Subject: Mixed mode methods
From: cschneid@cschneid.com (Christian Schneider)

Hi internals,

While some people are trying to make PHP a stricter language I'm also =
interested in making it a more flexible language by allowing to opt-in =
to advanced features for people who want it.
Please don't shoot this down just because you are not the target =
audience of such a feature ;-)

Toying around with PHP 8 I noticed that it is now impossible to have =
methods which can be called both statically and in an object.
This proposal brings back mixed mode methods both for extensions and a =
new syntax for user-land functions to explicitly allow it.

Motivation:
- Make migration of tried-and-tested mixed mode methods easier while =
having to explicitly declare it. So yes, unchanged code gets the new =
stricter semantics but updating code to the new (and from now on =
well-defined) behaviour can be done by simply extending the function =
definition. Having to rewrite such code to two different method names =
can be tedious and error-prone without big benefit.
- Allowing mixed mode methods as a form of name-overload in cases having =
to have two separate names for static/non-static is a WTF.
- Reviving things like
	$elements =3D DOMDocument::loadXML($html)->childNodes;
   instead of having to rewrite them to something like
	($dom =3D new DOMDocument)->loadXML($html);
	$elements =3D $dom->childNodes;
   by adding ZEND_ACC_ALLOW_STATIC to the method signature =
(ext/dom/document.c currently still contains code to handle both cases).

A first shot at an implementation was done using the syntax ?static and =
using isset($this) to determine the current mode:
class A {
	var $dynamic =3D 'dynamic';
	?static function mixedmodefn() { return isset($this) ? =
$this->dynamic : 'static'; }
}
allowing both (new A)->mixedmodefn() and A::mixedmodefn().

The implementation (including a test) can be found at
	=
https://github.com/php/php-src/compare/master...chschneider:optional_stati=
c

If people are interested I could create an RFC for this.

Regards,
- Chris