Auto populate drop down based on text box value

We are creating a form where user can add multiple rows and each row will have multiple fields. The first field in each row will be text box (TB) "product name " which will auto suggest product name to the user as they type (auto fill / auto suggest). Once user has typed in or as they type the product name in this text field, the second field which is a drop down (DD) called "Brand name", will get filled based on the value of the fist text field ("product name"). Further a third field, the "sub category" (SB) drop down will get filled based on the value selected in the second drop down filed ("brand name.") There will be more text boxes in the row but there is no inter connectivity. The connectivity is only between the first three fields in every row which are Product name (TB) Brand name (DD) Sub category (SB) ...Other text boxes The values in the first 3 fields will be fetched from a mysql database using Php.