Angular post没有访问目录中的index.php并返回301错误

In my angular project, I am trying to create a dummy api call. I created a directory api/auth and there is an index.php file in it. When I try to send post data to that file using http.post in angular, on first call it is showing 301 Moved Permanently error. But if I try to access the url using postman, then it is working. What is wrong here?

this.http.post('/api/auth', parameters, request.options)

I have set the rest of url as base path and it will append automatically.

If I try using the url /api/auth/index.php, then it will work without any issue.

Please help to fix this.