What does WeChat development Reply to success mean?

In the development documentation, what does this mean? How to reply to success? How to return a null string? I searched for all the information on the internet. I just excerpted this section and did not say how to do it. I really don't know what this means. Thank you.

In the development documentation

But what does this mean? How to reply to success? How to return a null string?

I searched for all the information on the internet. I just excerpted this section and did not say how to do it.
I really don't know what this means. Thank you.

Reply content:

In the development documentation

But what does this mean? How to reply to success? How to return a null string?

I searched for all the information on the internet. I just excerpted this section and did not say how to do it.
I really don't know what this means. Thank you.

If the code returned during normal push is an xml containing your reply content
When you do not want to reply to a message, but cannot respond within five seconds, you should directly reply to a success or empty string.
Note that the success here means that only outputting this item is equivalent to echo 'success '; not a response content is success's xml