i think your wrong brad no offence by this but by the code he provided $error_message must not be defined before this conditional or it it not in scope.
so by the code he provided and the by the error_reported message the logical standpoint is that he has not yet defined the variable $error_message.
But as you requested there could be more to this than the code he provided as i have a feeling it could be a scope or he just forgot to define the var.
Thisis why more than just the line needs to be provided.