Traits and redeclaring static properties

Hi everyone A few days ago we received a bug report about an inconsistency with traits and static properties. https://github.com/php/php-src/issues/10935 https://3v4l.org/Dll1m ``` class A { static $test; } class B extends A { static $test; } A::$test = 'A'; B::$test = 'B'; var_dump(A::$test, B::$test); // string(1) "A" // string(1) "B" ``` https://3v4l.org/SClLn ``` trait Foo { static $test; } class A { use Foo; } class B extends A { use Foo; } A::$test = 'A'; B::$test = 'B'; var_dump(A::$test, B::$test); // string(1) "B" // string(1) "B" ``` To summarize, a trait does *not* add a property to a class that has already inherited the same property from its parent. This makes sense for non-static properties, as redeclaring the property essentially has no effect. For static properties, however, there's a semantic difference in that redeclaring a static property creates a new slot in the current class that is separate from the parent's static property slot. This was never explicitly specified by the traits RFC. However, this sentence hints at the fact that the two examples above should behave equivalently. https://wiki.php.net/rfc/horizontalreuse > It is almost like a language supported and failsafe copy'n'paste mechanism to build > classes. I created a PR to align the behavior of the two examples. It targets the master branch to avoid any potential backwards incompatibility in a patch. https://github.com/php/php-src/pull/10937 Please let me know if there are any concerns about this change. Ilija