WeChat public platform background slow response how to reply to empty strings and then call the Customer Service Interface

What is the format of this empty string? Is it in the format of publicfunctionresponseTextcs () {echo & quot; return & quot;}? Why is the format of the empty string repeatedly sent? Is public function responseTextcs ()
{
Echo "";
Return "";
}
In this format? Why do I send repeated requests?

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What is the format of this empty string? Is public function responseTextcs ()
{
Echo "";
Return "";
}
In this format? Why do I send repeated requests?

It should be written like this... For more information about calling the customer service interface, see customer service ..

No one answered this question.
This is also the problem I encountered.
After echo "", there are other business processes, such as DB operations, which may lead to latency. My understanding is that Php is a single thread. Therefore, the solution is to use an asynchronous solution. However, php does not seem to have a good asynchronous solution to handle such a problem.