using html select as array

Hi list, In my system I have multiples choices of language that user selects using drop down menus. So I've named this dropdows language[] and grab it as php array, and with looo i insert it into mysql as registers. But now i need to put a text field that the user can type any language that is not in the dropdown. my question is how can i know when this was typed when i do the select to update the user itens. I mean, when i select and populate your preferences to update, how can i know that this info is from the input text??? Thank's Rodrigo