I'm building a content management sytem for my site, and I have the next problem.
The administrator is allowed to add, edit and delete authors. When he chooses the edit option, he gets a form with the current values (received from the database = MySql; I use PHP for this cms). The values auName and auEmail cannot be null ("not null"). But when the admin just deletes the values in the form, MySql (and Php too probably) thinks this is just empty ("") instead of null.

Is there a way to transform the "" value to a NULL value?

Thanks for any help,