Using the “multiple” Value in a list box

I have a database on a remote server, (SQL) which I populate by gathering data from an HTML form. I have a variable called Catagory that is a multiple select list. I am passing the information along to PHP-4 which in turn populates the database table. The issue is this.
The HTML is only submitting the last selected item in the catagory even though i select three items. I am under the assumption that I need to incorperate JAVASCRIPT to help me create a comma dilineated string to then pass along to the php. Can anyone help me with this one.

Thanks

JM