It should be placed at the top of your script is the simple, easy and most effective solution.
require and include both add the contents of the file to the script that calls them, just as if you had copy/pasted it by hand. The functions/contents in named file may only be conditionaly needed, probably are from the look of that message, and may otherwise cause problems. But without seeing them both all I can say is put it near the top of the script alongside the require statements for your common functions scripts, I take it you have those.
