I think that can easealy be done with stored procedure... I would suggest you to read this article HERE I think that's the answer on your solution.
Here is SQL Fiddle to see how that works on your problem...
here is your stored procedure
CREATE PROCEDURE addItem
(IN inkno INT, IN inddate DATETIME, IN inadded_Date DATETIME, IN inadded_By INT)
BEGIN
DECLARE SomeId int;
DECLARE CheckExists int;
SET CheckExists = 0;
SELECT count(*) INTO CheckExists from kitchenitems WHERE kno = inkno;
IF (CheckExists > 0) THEN
SELECT kno INTO SomeId FROM kitchenitems WHERE kno = inkno;
ELSE
INSERT INTO kitchenitems (kno,ddate,added_Date,added_By)
VALUES (inkno, inddate,inadded_Date, inadded_By);
END IF;
END/