Yes, indeed you should choose between Dr. Phillip Katz and Phillip Katz, Ph.D., just like Clive states. However, one should note well that Ph.D. stands for 'Doctor of Philosophy'; thus some doctors (Dr.) needn't be Ph.D's but can just as well be Doctors of Science or Doctors of Medicine, for intstance.
I'd just like to add another comment. The term 'philosophy' today is usually used in a rather specialized sense, but it has an older, broader, meaning of 'all knowledge'. We see this meaning, for example, in the famous quotation from Hamlet:
There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy.