根据在另一个下拉菜单中的选择，从DB中提取下拉选项

I have two dropdown lists as a part of a form I'm creating, both of which have options that are being pulled from a mysql database. I would like the options in the second dropdown to change based on the selection in the first dropdown. I know how to do this using Javascript when the second list is static, but I would like both dropdowns to dynamically pull from the database. Below is the HTML and Javascript I'm currently using. Any ideas would be great.I have two dropdown lists as a part of a form I