Does everyone who is doing a PhD has to dabble in philosophy to a certain extent?
The question is irrespective of the field of research.
No. This is a misinterpretation of what “Ph.D.” means. The full title of the degree is Philosophiae doctor, technically a doctor “of philosophy.” However, this does not mean "philosophy" in the modern sense, but rather someone who pursues knowledge (“lover of wisdom”—the source of "philosophy"), not necessarily someone who studies philosophy.
No. In fact, the vast majority of PhDs do not study philosophy in any reasonable sense.
From the Greek, "philosophy" literally means the "love of wisdom". If we define philosophy as a study that encompasses knowledge, language, and reason, then everything we study touches upon philosophy. So in this particular sense, the answer to your question is "yes".
However, for the vast majority of PhDs (other than in philosophy, theology, and other related fields) there is no requirement to take any philosophy courses or even to know how to spell Plato. So, in this particular sense, the answer to your question is "no".
It depends on what is your definition of philosophy. In my view philosophy is a discussion of 5 elements 1) Yourself 2) The nature 3) God 4) Life 5) Death If we go by above definition P.hd is studying on at least one aspect. If one can study and understand all above aspects then he is a philosopher. To answer your question. No most of the phd students don’t study philosophy.