Phd interview question Just wondering if anyone has ever been asked this question during a PhD interview: If you get a place without funding, would you be able/willing to self-fund? 

My interviewer said that it was compulsory to ask this question.
Short answer: Yes.

Slightly longer answer:
Some programs that aren't able to guarantee fully funding their students often ask this question just in case they run across some issues with securing funding from the school. Some programs ask this question during the interview but from my experience, most ask during the application process. For me personally, the question usually asked how much money I would be able to take out of my own pocket to pay for tuition (I always just wrote "0").

Since I'm not on the faculty of whatever program you applied to, I can't speak for your program, but they may take your answer into consideration for whether to accept you into the program or not.