Hi,
You should include some code it would be easier to see what is wrong.
But from the error message it seams like there is something wrong with the way you pass the data to the update method
Also, not 100% sure but I think DB_active_rec.php is the old (CI ver 2).
In CI 3 it is some thing like DB_query_builder.php.
A good decision is based on knowledge and not on numbers. - Plato