session_register()

I have been racking my brain with this for hours and I am not getting anywhere. session_register doesn't seem to be registering my variables. Several questions to see if I am even on the right track. Do you need to register a variable with the session before you assign it a value? session_register should return true if the variable was successfully registered? The variable name and it's value should be written to the file with the same name as session_id()? Jennifer