I am extending: XenForo_ViewAdmin_Node_List This class is not defined in the default software so I don't need to call the parent in my extended function. But there is the case of other addons also extending this class in which case a parent call needs to be in place. Because the parent may not exist I need some condition to check the existence of the parent function. I have tried a few things including method_exists() and is_callable() but it's not working. The 'parent' keyword doesn't seem to work for such a check in this context. Ideas?