Bug #73220 [Nab]: Classes implementing an interface can violate its method's signatures

Edit report at https://bugs.php.net/bug.php?id=73220&edit=1 ID: 73220 User updated by: phansys at gmail dot com Reported by: phansys at gmail dot com Summary: Classes implementing an interface can violate its method's signatures Status: Not a bug Type: Bug -Package: Scripting Engine problem +Package: Documentation problem Operating System: any PHP Version: 7.0.11 Block user comment: N Private report: N New Comment: http://php.net/manual/en/language.oop5.interfaces.php#language.oop5.interfaces states in a note: "The class implementing the interface must use the exact same method signatures as are defined in the interface. Not doing so will result in a fatal error." Which doesn't seem to mention LS principle in any way. Previous Comments: ------------------------------------------------------------------------ [2016-10-02 13:16:04] phansys at gmail dot com So, should I create another bug report for Object Interfaces documentation? http://php.net/manual/en/language.oop5.interfaces.php#language.oop5.interfaces It states in a note: "The class implementing the interface must use the exact same method signatures as are defined in the interface. Not doing so will result in a fatal error." Which doesn't seem to mention LS principle in any way. ------------------------------------------------------------------------ [2016-10-02 06:12:09] bradyn at bradynpoulsen dot com Adding another optional parameter is totally allowed by LSP. As long as the implementing class allows you to call test() or test('someValue') as specified by the interface, the class is honoring the method signature. However, if class B were defined as: class B implements A { public function test($one = null, $two) { var_dump($one, $two); } } it would then be violating the signature in requiring the 2nd parameter to be passed. As such, you would receive the expected result mentioned above. ------------------------------------------------------------------------ [2016-10-01 21:50:49] rasmus@php.net Adding additional default values does not violate LSP (Liskov Substitution Principle) in that in your example, B can be used in place of any other class that implements A and as such it is entirely compatible with A and there should be no error. ------------------------------------------------------------------------ [2016-10-01 19:53:14] phansys at gmail dot com Description: ------------ Classes implementing an interface can violate its method's signatures by adding more arguments with a default value. Test script: --------------- interface A { public function test($one = null); } class B implements A { public function test($one = null, $two = null) { var_dump($one, $two); } } Expected result: ---------------- Fatal error: Declaration of B::test($one, $two) must be compatible with A::test($one = NULL) Actual result: -------------- No error. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=73220&edit=1