When sending a POST request to php, the Nginx script gives a 404 or 502 error. Why?

Question

PHP

There is a php script on nginx that receives data via a POST request. But when sending a POST request to php, the Nginx script gives a 404 or 502 error.
Has anyone experienced this?

Answer 1

see error_log

Answer 2

Show me the nginx config. What does php handle? Are there any rewrites?
Enable debugging in the nginx logs and in the logs of what php handles.