Multiple select box and form submitting

i apologize in advance if the answer to my question is glaringly obvious. i've got a multiple select on a form and want to find out *all* selected values. the form looks like so: <SELECT NAME="form[category]" MULTIPLE> <OPTION VALUE="0">First <OPTION VALUE="1">Second <OPTION VALUE="2">Third </SELECT> when the form submits, $form['category'] is not an array of selected values, but rather a single value. even if i select two or three things, $form['category'] is still one value. can anyone tell me how to get a list of all selected values in the box? thanks in advance...