On the Mayflower blog there's a new post looking at the upcoming traits support PHP 5.4 will have to offer. (Note: original post in German)
PHP 5 was a big step in the right direction and today resembles the object-orientation of Java very much. At the end of June 2011 one more step was made, not based on Java, but from another popular language - Scala. The new language feature called Traits allow class and cross-code reuse with no vertical transmission. It is basically a relatively simple mechanism, which is explained below using a simple example.
Their examples are a "before" and "after" of the same functionality - creating a controller that can respond with a JSON message. The first example shows a simple controller that can respond in JSON, a JSON class that can work with HTTP and a User class that implements the Serializable interface on the JSON namespace. The second example redefines the Serializable interface as a trait that can be used inside the User class rather than inherited by it.
There's also a brief look at using multiple traits in one class and what to do about naming conflicts that might pop up and the prioritization method that's been put in place to help.