Well abstract classes still have their uses, and I actually prefer it than traits. Traits in PHP are not like they are in Scala, they are more close to mixins. The implementation is static access and traits can be converted to static methods with ease, which is a sign of something bad. It can be beneficial to use traits sparingly, but abusing traits and use it in places of abstract classes can result in undesirable consequences. Read this article if you want to read the pitfalls of traits in PHP:
http://www.whitewashing.de/2013/04/12/traits_are_static_access.html