如何判断数据库查询或自动电子邮件等失败的系统进程是否值得向用户发送错误消息？

I'm thinking through all the points in my PHP application where it performs some sort of system process like database queries, or sending out an email, and I'm wondering if at all these points I should be notifying a user when something goes wrong. There are so many points where an application can fall apart, that I'm having trouble determining if it is worth it to notify the user. Is it better to have some sort of logging in place, where every few days I just monitor the logs? Is there a standard approach for large-scale applications?I'm thinking through all the points in my PHP a