Boban Acimovic has recently posted a tutorial showing you how to use traits in a Zend Framework 2 application to inject additional functionality into your pre-existing classes.
There are several tutorials on the Internet which explain how to use interface based dependency injection in Zend Framework 2. The idea is to make an initializer, figure out which interfaces a class implements and then inject appropriate dependencies using setters defined in the interfaces. Bad part about this is that in each class you implement such an interface you have to declare a property which would hold the injected object and also to implement the setter for it, which is defined in the interface, by the way. In order to simplify this further it is possible to write trait for each interface, but then why should not use just traits? Why do we need interfaces? Is this possible at all?
He includes some example code showing how to set up dependency injection for the traits (via a custom injector based on the "InitializerInterface") and make the autoloading easier. He shows how to add this to the provider configuration as an "initializer" and create the first example trait, a checker for data in user passwords. He then drops the functionality into a service class just by using the "use" keyword and the trait name.