Multi Select Box to MySql DB Table

Generate multi select box from data in db, then when submitted, each selection is written to a db table as it's own record, each tied together by a common record id.

<?
//Create multi select box, pulling data from db
                $sql = "SELECT id,name FROM table ORDER BY name ASC";
                $result = mysql_query($sql);

                if($result && mysql_num_rows($result)>0)
                {
                ?>
                <select name="id[]" size=5 multiple><option value=0 selected>Select Name...</option>
                <?
                for($i=0;$i<mysql_num_rows($result);$i++)
                {
                $arr=mysql_fetch_array($result);
                echo "<option value=" . $arr['id'] . ">".$arr['name'];
                }
                echo "</select>";
                }else
                echo "No Names in DB";
?>

<?
//when multi select is submitted from form, this part processes it

$id = $_POST['id'];

foreach ($_POST['id'] as $id)

        $result_system = mysql_query("INSERT INTO diff_table (diff_id,id) VALUES ('$diff_id','" . $id . "')")or die("Insert Error: ".mysql_error());

?>