Java has default methods, Scala has traits. Is there a way to get the effect that given method in PHP interface has body? Assuming I have total control over the interface, the method, everything.
PHP also has access to Traits as of PHP 5.4.0.
Read more here.
That's the point actually. Interfaces do not implement the body of their methods , that's why you create classes which would implement them.
The purpose of interfaces is to provide an uniform way to interact between classes implementing an interface, but there is nothing that could force their behaviour.
Interfaces represent a specific kind of constraint which is totally different from inheritance
EDIT : I saw your comment but it seems that it was deleted or something. I'm sorry if you felt like i was "paraphrasing"/patronizing what you did say but I can't say more since it's pretty "simple" because of a straight fact