Writing MySQL Update Query with NULL value

I'm trying to write a MySQL UPDATE query where one or more variables may be NULL. So, I'm trying something like: $last_name = $_POST['last_name']; $first_name = $_POST['first_name']; $suffix = $_POST['suffix']; $suffix = empty($suffix) ? NULL : $suffix; $phone = $_POST['phone']; $phone_index = $_POST['phone_index']; $update_query = "UPDATE 'phones'

                   SET 'last_name' = $last_name, 'first_name' = $first_name,
                   'suffix' = $suffix, 'phone' = $phone
                   WHERE 'phone_index' = $phone_index;";

However, when I echo out this query, I get: UPDATE 'phones' SET 'last_name' = Doe, 'first_name' = John, 'suffix' = , 'phone' = 123-456-7890 WHERE 'phone_index' = 323; I think, for this to properly update the record, it should be: UPDATE 'phones' SET 'last_name' = Doe, 'first_name' = John, 'suffix' = NULL, 'phone' = 123-456-7890 WHERE 'phone_index' = 323; What am I doing wrong?

     -----===== Bill =====-----
-- 

Nothing is so bad that it can't get worse.