hello aspirant,

YES, you can do Phd after completing PG Diploma course.

After completing your PG diploma, you have two options for pursuing your PhD : The PG diploma must be recognised by the Association of Indian Universities as comparable to a master's degree programme, and you must score at least 55 percent overall, among other requirements.

Further, to know more information about the Phd course, you can follow the below mentioned link to know more about it in detail : https://www.careers360.com/courses/ph-d-doctor-of-philosophy

I hope that this will help.