Hey Muneer

See, there is no need for you to do a phd to become an ias officer. If you want to do a phd then you can first clear ias exam first as the maximum age to apply for IAS is 32 years. It takes around 10 years(minimum) to get a UG, PG and then PhD degree in India (that means you will probably be 28 years old if you give your 12th at the age 18 and do not drop for even a year). Clearing IAS is not that easy hence that will take some time too. Also, what is the use of getting a PhD if you have to become an IAS officer.

The best path according to me will be to first clear graduation and then IAS after which you can do PhD. All the best.