$pdo is undefined. You're not declaring it inside the function, and it isn't being passed in as an argument.
You may also get this error from active, unbuffered queries still active.
I got to say that you've encountered a pretty interesting error, so let's try some things to pinpoint the cause.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.