Looks like something is filtering out PHP code insertion. I don't know that plug-in so don't really know what you're doing, but if it's something you are entering in a configuration/set-up page for that plug-in, I don't think that's the point where you want to be inserting PHP code. If you need to customize it in that way, you probably will have to actually go into the source code of the plug-in to modify its behavior.
"Please give us a simple answer, so that we don't have to think, because if we think, we might find answers that don't fit the way we want the world to be."
~ Terry Pratchett in Nation