Clear POST variables

I have a page that submits form information into a database, and all is good, but someone testing the page pointed out something to me that I didn't notice. I have a form that sends you to another page that submits the data into a database. If you refresh the page, the information is submitted again. Here is what I have.

        $name = $_POST['name'];
        $address = $_POST['address'];
        $city = $_POST['city'];
        $state = $_POST['state'];
        $zipcode = $_POST['zipcode'];
        $phone = $_POST['phone'];
        $notes = $_POST['notes'];

        $query = "insert into Locations
                                (name, address, city, loc_state, main_phone, zipcode, notes)
                                values
                                ('$name', '$address', '$city', '$state', '$phone', '$zipcode',

'$notes')";

                                mysql_query($query, $link) or die (mysql_error());

How do I clear out the POST variables, or the variables that I have set from the POST variables, so that when the page is refreshed it will not resubmit. I have tried unset() and have tried to set it to and empty value, but it doesn't seem to work. Thanks.