Is it better to be fired or to quit?

I received a performance improvement plan at a job X I hate a few weeks ago and I don't think I am meeting the goals, despite how hard I try. I have been looking for a new job for about two months now and have had some interviews and no offers yet. I think I will be fired if I mess up the PIP. Is it better to quit before I can get fired? Or keep risking it? And how would I disclose that to my future interviews, if when I applied I said I was still working at job X?

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