Emmanuel Valverde Ramos

but also add a way to have multi-inheritance in PHP.

I consider that allowing multiple inheritance is a mistake, since inheritance is something that in more than 90% of cases is a premature and erroneous abstraction of reality.

• Interface shall stay light, pure contracts defining expectations, else they are just abstract classes with multi-inheritance.
• If multi-inheritance is the subject, a specific RFC shall be done on this.
• An other away might be to dig back this RFC to add interface to traits: https://wiki.php.net/rfc/traits-with-interfaces

It looks pretty much the exact function as abstract class. I still think interfaces/contracts should not include any concrete implementation