I feel sorry for anyone who has invested time and money into such a worthless piece of paper. PHDs were useful in the past when very few people were able to afford or have the time to get such a valuable piece of paper. Nowadays that people are willing to go into debt and burn lots of time, almost any idiot can get a PHD.
Likely a PHD student pictured above.
It makes sense to get into debt if you're likely to get bigger return, so in that case the debt is merely an investment. However, a PHD is a horrible investment because the chances of it giving back what you invested are unlikely. There is simply too few jobs and the competition is fierce, you might as well play the lottery, at least you'll lose a lot less money and the prize is bigger anyways.
However, if you are going for a PHD because you love what you are studying and can't imagine doing anything else, then go for it.
Don't expect it to be a walk on the park though.