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