These tips may help you. I am sorry that I will not be providing you with codes since I have not one ready, and it really takes time to create one. But I will be giving you hints toward which you can move your way to reach the success.
1. First of all create a MySQL database and possibly create two tables, the one for the year and the another for film name or something like that, you are able to create one that seems more logical to you.
3. The third step will be if you are going with creating an AJAX script. Create a function that will submit the Value of first selectbox on a onchange() event.
4. Create a page in php without any html inside it. This page will receive this data (the value of Selectbox1) and process it using MYSQL query to get a list of the array that will be storing the name of the Movies. Echo this data using this kind of code as example:
foreach($dataarray as $moviename)
5. In the ajax script, simply put this code in a block defined with ID name like this:
if(xmlhttp.readyState == 4 && xmlhttp.status == 200)
document.getElementById("movieid").innerHTML = xmlhttp.responseText;
and, in the html part define something like this:
6. Now you have your very own professional looking Select Box System, in which the Items displayed in one box will depend on the item selected in another box.
Hope it has helped you. I will possibly post the code if I get time to write one very soon.