how i do it is to insert record into the joke table, then make a quick
select query like this "select max(id) as id from joke - this will give you the last id entered, the only flaw with this approach is if a insert query sneaks in-between
your insert and the select statement, so far i have not had any trouble with this.
store this value then repeat this for your category table as well, if you are allowing them to enter...