public function doTheJobChild($num, $callback, $params = array()) {
        if (!$callback instanceof CallbackHandler) {
            $callback = new CallbackHandler($callback);
        }
        if (!is_array($params)) {
            $params = array($params);
        }
        $this->callbackChildren[$num] = $callback;
        $this->callbackParamChildren[$num] = $params;
        return $this;
    }