How many college units must a student complete to attain a Phd?

I’m getting close to finishing my AA in Advertising and Graphic Art. I have 118 units completed. This is because I changed majors twice and also took a lot of electives that I really enjoyed.
I was wondering (because someone once jokingly said that I should have my Phd by now, with all of the time I’ve been in school), how many units does a person need to get their Phd?