PHP does not have concept of mixins, however it has [traits][1] which look like mix of traits and mixins from hack/scala:

* Can define properties.
* Can define constructors.
* Can define abstract methods.
* Does not support inheritance.
* Traits are not types.

> Are these definitions accurate for any OO language or just for the above mentioned ones ? 

I don't think that there is even a single thing that will work in the same way in all OO languages. Even some basics like inheritance and interfaces have some variations, not mention more blurred constructs like traits/mixins.


 [1]: http://php.net/manual/en/language.oop5.traits.php