[php-src] Issue #13278: Void can only be used as a standalone

Issue: https://github.com/php/php-src/issues/13278 Author: SVGAnimate ### Description The following code is valid: ```php <?php function zoo() {} function foo():void {} ``` The same behavior exists for `never` The following code: ```php <?php function foo(void) {} foo(); ``` Resulted in this output: ``` Parse error: syntax error, unexpected token ")", expecting variable ``` But I expected this output instead: ``` ``` Since this code is valide in c : ```c void foo(void *a) {} ``` I expecte this code is valide : ```PHP function foo(void $a) {}// Fatal error: void cannot be used as a parameter type ``` Also : ```php <?php function foo(int|void $a) {}// Fatal error: Void can only be used as a standalone type ``` Is there an RFC about parameters who accept a mixed value or an optional value ? ### PHP Version PHP 8.1.12 ### Operating System _No response_