我可以在PHP函数中添加javascript警报吗？如果有，怎么样？

假设您的意思是您希望在服务器时从浏览器弹出警报在你的PHP代码中达到某一点，答案是否。

Assuming that what you mean is that you want an alert to pop up from the browser when the server reaches a certain point in your php code, the answer is "no".

当服务器运行你的php代码时，没有与浏览器的联系（直到响应开始回来了）。在某些情况下，服务器可能会将内容流式传输回浏览器，在这种情况下，可能会有一些商定的约定，服务器要将内容流标记为立即提醒消息，但是我不认为这就是你在这里问的问题。

While the server is running your php code, there's no contact with the browser (until the response starts coming back). There are situations in which a server may be streaming content back to the browser, and in such a case it'd be possible to have some agreed-upon convention for the server to mark the content stream with messages to be alerted out immediately, but I don't think that's what you're asking about here.