how to use composer with docker-compose

If you look at composer/composer:php7 Dockerfile, then you will see, that it is based on php:7.0-alpine and it doesn't seem like fpm is included. So, you could use composer/composer:php7 as base image to install php-fpm on top of it.

So, since you do the mapping of your project in all three containers, running composer install in one container should result in the changes be visible in all three containers.

Me personally, I do not see a point in segregating PHP and nginx into 2 different containers, because one is highly dependable on another. And mapping your app into both containers is also a perfect example of nonsense. That's why I maintain my own public build of nginx+php Docker image. You can check it out here. There are more builds with more flavors. And they all come with composer inside.

I set up my docker-compose.yml file so one docker instance would use the composer/composer image and execute composer install within a shared container. All of the other images would then be able to access the vendor directory that composer created. The tricky part was realizing that the composer/composer image assumes that the composer.json file will be in an /app directory. I had to override this behavior by specifying my shared container as the working_dir instead:

version: '3'services:  #=====================#  # nginx proxy service #  #=====================#  nginx_proxy:    image: nginx:alpine    networks:      - test_network    ports:      - "80:80"      - "443:443"    volumes:      # self-signed testing wildcard ssl certificate      - "./certs:/certs"      # proxy needs access to static files      - "./site1/public:/site1/public"      - "./site2/public:/site2/public"      # proxy needs nginx configuration files      - "./site1/site1.test.conf:/etc/nginx/conf.d/site1.test.conf"      - "./site2/site2.test.conf:/etc/nginx/conf.d/site2.test.conf"    container_name: nginx_proxy  #===============#  # composer.test #  #===============#  composer.test:    image: composer/composer    networks:      - test_network    ports:      - "9001:9000"    volumes:      - "./composer:/composer"    container_name: composer.test    working_dir: /composer    command: install  #============#  # site1.test #  #============#  site1.test:    build: ./site1    networks:      - test_network    ports:      - "9002:9000"    environment:      - "VIRTUAL_HOST=site1.test"    volumes:      - "./composer:/composer"      - "./site1:/site1"    container_name: site1.test  #============#  # site2.test #  #============#  site2.test:    build: ./site2    networks:      - test_network    ports:      - "9003:9000"    environment:      - "VIRTUAL_HOST=site2.test"    volumes:      - "./composer:/composer"      - "./site2:/site2"    container_name: site2.test# networksnetworks:  test_network:

Here is how the directory structure looks:

certs    test.crt    test.keycomposer    composer.jsonsite1    app    public    Dockerfile    site1.test.confsite2    app    public    Dockerfile    site2.test.confdocker-compose.yml