In the United States, someone a "doctor of philosophy," abbreviated "Ph. D." is rarely a philosopher. For historical reasons, it is the name given to an advanced degree. A common sequence is "bachelor's degree," "master's degree," "Ph.D."
A bachelor's degree often takes four years, and often requires just taking and passing courses with good grades. After you get a bachelor's degree, you might go on to get a master's and a Ph.D.
A Ph.D. is always "in" some field. You might have "a Ph.D. in biology" or "a Ph.D. in physics" or "a Ph.D. in economics." You would be a biologist, or a physicist, or an economist.
In the US in 2019/2020, 11,000 people got Ph.Ds in engineering. 700 got Ph.Ds in "philosophy and religious studies."
A Ph.D. takes a variable length of time, Taking courses is only a small part of it. Here's how Columbia University describes their Ph.D. program in philosophy:
"The purpose of earning a Ph.D. in Philosophy is to become an independent scholar as well as a teacher of the subject. Perhaps the single most important accomplishment during the Ph.D. is the writing of the doctoral dissertation, which is typically a student’s first substantial and original scholarly contribution to Philosophy. The coursework that is undertaken in advance of the dissertation is meant to serve as preparation both for writing the dissertation and for teaching. In addition to coursework and the dissertation, Ph.D. students at Columbia are required to assist in the teaching of undergraduate courses as part of their doctoral training."
In the United States, some Ph.D. degrees are highly "marketable skills." Someone with a Ph.D. in electrical engineering can probably get an excellent job.
To get a Ph.D. in philosophy, you need to have a real love of philosophy. Most jobs in philosophy would probably involve teaching philosophy at a university. You would also need to figure out how to pay for many years of tuition.