This PIP thing sounds so familiar. I also kena-ed this at my previous company.
In my case, I was just with the company for about 1.5 years and my first appraisal (half year after joining) was excellent and I was given a rather good increment and bonus even though I wasn't even eligible for bonus/increment. But fast forward to 1 year later, suddenly, during year-end performance review they told me I was not performing. First reaction is of course, anger. Was in a room with my direct manager and dept head and so I didnt even bother to look at my direct manager. Instead I looked at the dept head and asked her, if there really was an issue with my performance, why wasnt this highlighted to me by my manager during our weekly 1-1 meetings? My manager just kept silent. After the dept head left the room, my manager's remark to me shocked me, she said "I am not even sure if you will still come to work tomorrow after this conversation". OMG what a stupid remark from here right? Even though I was sad and affected, but the work still needs to be done and I will continue to deliver my work in a professional manner, despite the most ridiculous and unexplanable comversation that just happened.

Anyway it didnt take me long to decide I did not want to work for such ridiculous and unprofessional people. I did not like the company culture in the first place. It's a local company and all along I worked for big foreign names. And after the rather unexplainable and puzzling year-end review, I decided to job hunt. The final straw came when 2 months after the year end review, it was bonus payout time and they did not give me a single cent of increment or bonus. And then my manager told me that they will start me on the PIP soon. Obviously I refused to start on this programme, for it will be a way for them to say I did not meet their standards after 3 months, and it will tarnish my record. So I job hunted really hard and resigned soon after.

My advice: do not start on the program if you can. Walk away with your head held high and remember, there are plenty of other jobs out there, and may you find a new job quickly. Good luck!