Murphy doesn't have a PhD, he completed Medical School(MD) after which one is given the title "Doctor".
After med school, new doctors apply for residencies of a specific specialty e.g Surgery, Internal Medicine, Radiology, psichiatry.
A residency is both employment and education. Ater this is completed, the resident usually undergoes an exam to become board certified and becomes an Attending. Further training into a sub specialty e.g Cardiothoracic, plastics can be done.