note 34194 deleted from language.oop.object-comparison-php5 by sniper

Note Submitter: hobbit@euthanized.org ---- Interestingly thing I found PHP5's interface support... Let me set up the example: You have an interface called IPrintable You have a class called A that implements IPrintable You have a class called B that is derived from A You have a function called PrintObject (IPrintable $obj) So the question is do you have to explicitly say that B implements IPrintable in order to pass objects of class B to PrintObject? Or is the interface implementation implied by the fact that its parent class implements the interface? The answer is that it is implied by the fact that A implemented the interface (which is safe to do and makes sense.) So you do not *have* to explicitly state that B implements the interface in order to pass objects of class B to PrintObject. What's interesting though is that you *CAN* explicitly say that B implements the interface and not actually implement the interface in B...and PHP will accept it because A implements the interface. If you do actually implement the interface and implement new functions for B...PHP will use the functions in B for an object of type B (only climbs as high as it needs to up the object hierchy to find a given method/methods.)