problem with file mounts in Nginx and php fpm containers - php

Question

I have two containers:
laravel with php:8.1-fpm-bullseye container exposed on 9000
nginx with nginx:1.23.1
nginx uses fastcgi_pass directive in configuration file
Question:
why do i need to also mount my app source code to nginx /var/www/html directory when all nginx does is that it turns http request to fastcgi request and passes them to laravel container? ( I commented out try_files directive in configuration but I'm still getting 404 response from nginx)
./nginx/nginx-default.conf:
upstream backend {
server laravel:9000;
}
server {
listen 80;
listen [::]:80;
server_name _;
error_log /var/log/nginx/error80.log;
access_log /var/log/nginx/access80.log custom;
return 301 https://$host$request_uri;
}
server {
listen 443 ssl;
listen [::]:443 ssl;
ssl_certificate /etc/ssl/certs/localhost.crt;
ssl_certificate_key /etc/ssl/private/localhost.key;
root /var/www/html/public;
error_log /var/log/nginx/error443.log;
access_log /var/log/nginx/access443.log custom;
index index.php;
location / {
try_files $uri $uri/ /index.php?$query_string;
}
location ~ [^/]\.php(/|$) {
try_files $uri =404;
fastcgi_pass backend;
fastcgi_index index.php;
fastcgi_keep_conn on;
fastcgi_split_path_info ^(.+?\.php)(/.*)$;
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param PATH_INFO $fastcgi_path_info;
fastcgi_param REQUEST_METHOD $request_method;
fastcgi_param CONTENT_TYPE $content_type;
fastcgi_param CONTENT_LENGTH $content_length;
fastcgi_param REDIRECT_STATUS 200;
}
}
./docker-compose.yml:
version: "3.8"
services:
user:
container_name: user
build:
context: ./
dockerfile: Dockerfile.development
volumes:
- ./:/var/www/html:rw
networks:
- user
user-nginx:
container_name: user-nginx
build:
context: ./nginx
dockerfile: Dockerfile.development
volumes:
# - ./:/var/www/html:rw # here !
- ./nginx/nginx-default.conf:/etc/nginx/conf.d/default.conf:rw
- ./nginx/nginx.conf:/etc/nginx/nginx.conf:rw
- ./nginx/logs:/var/log/nginx:rw
networks:
- user
depends_on:
- user
networks:
user:
driver: bridge
./nginx/Dockerfile.development:
FROM nginx:1.23.3
USER root
RUN usermod -aG root nginx
EXPOSE 80 443