FUCK THE POLICE
911 EVERY DAY
It all depends on your research project; how well it goes, how long each section takes to complete, whether or not your committee feels you've done enough to make a significant contribution to your field, etc., etc.
In physics a reasonable estimate could be that it would take you about five years. Depending upon where you go and what your project is. Other requirements are more fluid -- course requirements at this level generally are relatively minimal but other things like your qualifying exams and comprehensives, which vary from department to department, never mind institution to institution, may take more or less time. Then you'll also probably be involved in teaching undergraduates or acting as a teaching assistant. Frankly I learned more about statistics in depth by teaching it.
Well, I could probably make more money just on engineering without even having to go PH.D, which is why I'm hesitant about it, even though I love astrophysics. But I have a couple of years to decide.