Creating drop-down menus

Hello, I am making an application using PHP/Javascript/mysql and had a question. Sometimes I need to use javascript to fill a drop down box based on the value of a previous drop down box. However, the information to fill the latter is stored in mysql and can be a lot, what I have been doing is that, using PHP, I create hidden fields with all the possible information that might be needed to fill the second drop down. For example, the user chooses a bank from a drop down, and then a list of clients is displayed on the following drop down. I use PHP to read all clients from all the banks and put that as hidden fields on the html page. It is very cumbersome. I do not want to read the database (which changes dynamically) from javascript directly due to confidentiality and because a lot of care has been taken to create the appropriate queries with checks and protect misuse of the information using PHP. My questions are: 1) Do people just normally use hidden fields to store possible information to fill the drop downs? 2) any suggestions? Thanks in advance, Ramiro