This is quite complicated to install, and you need to follow the instructions exactly as posted.
You obviously installed the hack wrongly. I suggest you uninstall the hack, and redo the installation very very carefully. It works.
As for removing the variables - just find and delete the code in the instructions - they are 2 variables that need to come out of there, to be placed elsewhere in a new query.
If this sounds complicated, I suggest installing some easier hacks, to get a better understanding of PHP, before attempting this. Like I said, it's complicated. But if you follow the instructions closely, it works.