The question is the same as the title.
In order to avoid the x-y problem, let’s talk about the original problem:

We have a local verification service. There is no problem in calling this service directly through the php script process. However, calling the php process through the page and then calling the verification service, the php process will receive a 504 response. Error, but the nginx of the verification service has no relevant logs.

Since there is no log, I think it is not a problem with the verification service nginx, but where did the 504 report come from? Please ask God to clear up the confusion.