Hi there impact,
Just doing this sort of thing myself! The thing I notice first is this:-
Shouldn't it be:-
You have declared the function as:-
protected function dbcon
And you have it there all lower case, try altering the other calls to the same thing ;) as the other instance has it with the 'c' in upper case 'C'.
I'm not too sure on the use of $this in this instance though as you are extending the class, it may well be right, I haven't got that far yet!
Pop the error checking on (error_reporting(E_ALL);) and I'm sure you will see some kind of notice being flagged up as you stand now
Hope this helps,