[...]
networks:
  app:
    name: "monbeausite"
    [...]

services:
  app:
    container_name: monbeausite-app
    image: php:8-fpm-alpine
    volumes:
      - monbeausite:/opt/monbeausite:ro
    networks:
      - app
    restart: unless-stopped

  web:
    [...]
    networks:
      [...]
      - app