100% Abstract class vs Interface

Is there a reason to use a 100% abstract class and not an interface ? Can you give me a good example when to use both so I can grasp the concept a little?

Update: 100% Abstract class -> abstract class with only abstract methods. I'm curios if there are differences between php and java regarding this aspect.

Update2: Even if I understand most of the reasons I'm more interested in the conceptual more than technical reasons.