PHP 5.4.0 released

There's plenty of reason to have them even with multiple inheritance. Mixins can implement part of one or more interfaces, can include new members and methods, and -- this is most important -- can freely call into the class using the mixin.

In C++, which has no mixins, it is common to use a template to implement a mixin. Unfortunately it is not a "real" mixin due to various limitations the inheritance-based approach imposes. You can work around most of those with a lot of overly verbose syntax using CRTP, but it'd be nice if you didn't have to.