Unfortunatly, when I try to Verify/Upload, an error is given which states that 'sdErrorCheck was not declared in this scope.
Does anybody knows why and what I should do?
Because it wasn't, and you should declare it in that scope.
You are trying to call that function, but you have not defined that function.
I'm pretty sure that i will never equal a smiley face, so you should delete all that code.