Depends on the PhD, try and find out as much as possible about the research and your potential supervisor, their students will likely be very honest! Also, consider if it’s worth it in the industry you’ll likely end up in (It sounds like it would be). I’m in bio-med engineering and I believe now a Master’s would have suited me better.
I can’t wait to finish mine, currently writing up and just beginning to not regret doing it again.
I would say the majority of people in my office are your age, 30 definitely isn’t too old to start a PhD.