SELECT
        users.id
    ,   IFNULL(t_up.score, 0) - IFNULL(t_down.score, 0)AS 'invites'
    ,   IFNULL(t_down.score, 0) + IFNULL(t_up.score, 0) AS 'score'
FROM users
    LEFT JOIN
        (
            SELECT
                    (COUNT(*) * -1) AS 'score'
                ,   invited_by AS 'id'
            FROM users
            WHERE
                (class = 0 OR enabled = 'no')
            GROUP BY invited_by
        ) AS t_down
    ON
        users.id = t_down.id
    LEFT JOIN
        (
            SELECT
                    COUNT(*) AS 'score'
                ,   invited_by AS 'id'
            FROM users
            WHERE
                class > 1 AND enabled = 'yes'
            GROUP BY invited_by
        ) AS t_up
    ON
        users.id = t_up.id
WHERE
    class = " . $class . "
    AND enabled = 'yes'
    AND warned = 'no'
    AND NOT freeze_invites = 1
    AND invites < " . $max . "
    AND invitedate <= (NOW() - INTERVAL " . $days . " DAY)";