Auto-append items from a select list

Question

I have a list of different items within a select multiple list and I want to auto-append to a form that a user submits.

HTML of category multiple select list:

<select name="category[]" size="4" multiple="multiple" id="group">
    <option value='7'>Faculty</option>
    <option value='8'>Staff</option>
    <option value='6'>Students</option>
</select> 

I want to do something like:

<input type="hidden" name="category[7,8]" />

This will automatically assign the submission to the appropriate selected list items from within category[], without them ever seeing it.

This is stored within a database, so I need to accomplish it this way.

I know this does not work, but this should give you an idea of what I am trying to do.

Answer 1

I believe this could be accomplished using a Javascript library (such as jQuery) to handle the change on the Selections and append/update the items in your hidden field. You could then also use Ajax to update your database with the selection when necessary.

Your specific requirements might not allow for the above though. Some additional information would be helpful for those viewing such as what backend you're using (php, asp.net, or if it is just static html) and if you are currently using javascript (or a library) to assist you in any other tasks.

I'll try to check back on updates to see if I can be of more specific help. (Note: I think I'm too low of reputation to be able to post this as a comment at the moment so had to do an answer instead.)

Answer 2

A successful multiple-select control just gets submitted as having multiple values. E.g., if you selected "Faculty" and "Staff" in your list, what gets submitted is something like:

category[]=7&category[]=8

You can replicate this (at least in Firefox, haven't tested elsewhere) with two hidden inputs:

<input name="category[]" value="7" type="hidden"/>
<input name="category[]" value="8" type="hidden"/>