PHP 扩展对 docker-compose 中的 Composer 容器不可用

我使用 docker-compose，并在一个项目中拥有多个容器：Nginx、PHP、Composer 和 nginx。一切都很好，除了一件事：作曲家不工作。我正在尝试安装一个使用 GD 扩展的作曲家项目，该项目安装在 PHP 中（在 PHP 容器内使用 php -m 确认）。然而，composer 容器没有“看到”这个扩展并抱怨它不存在。我怎样才能将这两者联系起来？

docker-compose.yml：

version: '2'
services:
    web:
        image: nginx:1.15.1
        volumes:
            - ./.docker/conf/nginx/default.conf:/etc/nginx/conf.d/default.conf
            - ./html:/var/www/html
        ports:
            - 8888:80
        depends_on:
            - php
            - db
    php:
        build: .docker
        volumes:
            - ./.docker/conf/php/php.ini:/usr/local/etc/php/conf.d/php.ini
            - ./.docker/conf/php/xdebug.ini:/usr/local/etc/php/conf.d/xdebug.ini
            - ./html:/var/www/html
    composer:
        image: composer
        volumes:
            - ./html:/app
        command: install
        depends_on:
            - php
    db:
        image: postgres:10.4
        environment:
            - POSTGRES_DB=test
            - POSTGRES_USER=test
            - POSTGRES_PASSWORD=test
        ports:
            - 5432:5432
        volumes:
            - ./.docker/conf/postgres/:/docker-entrypoint-initdb.d/

    adminer:
        image: adminer
        ports:
        - 8080:8080

Dockerfile：

FROM php:7.2-fpm

RUN apt-get update && apt-get install -y \
        libfreetype6-dev \
        libjpeg62-turbo-dev \
        libmcrypt-dev \
        libpng-dev \
        libicu-dev \
        libpq-dev \
        libxpm-dev \
libvpx-dev \
    && pecl install xdebug \
    && docker-php-ext-enable xdebug \
    && docker-php-ext-install -j$(nproc) gd \
    && docker-php-ext-install -j$(nproc) intl \
    && docker-php-ext-install -j$(nproc) zip \
    && docker-php-ext-install -j$(nproc) pgsql \
    && docker-php-ext-install -j$(nproc) pdo_pgsql \
    && docker-php-ext-install -j$(nproc) exif \
    && docker-php-ext-configure gd \
        --with-freetype-dir=/usr/include/ \
        --with-jpeg-dir=/usr/include/ \
        --with-xpm-dir=/usr/lib/x86_64-linux-gnu/ \
        --with-vpx-dir=/usr/lib/x86_64-linux-gnu/ \

Error:

Starting test_app_db_1      ... done
Starting test_app_php_1     ... done
Starting test_app_adminer_1 ... done
Recreating test_app_composer_1 ... done
Starting test_app_web_1        ... done
Attaching to test_app_adminer_1, test_app_php_1, test_app_db_1, test_app_web_1, test_app_composer_1
php_1       | [12-Oct-2018 21:26:47] NOTICE: fpm is running, pid 1
php_1       | [12-Oct-2018 21:26:47] NOTICE: ready to handle connections
adminer_1   | PHP 7.2.1 Development Server started at Fri Oct 12 21:26:47 2018
db_1        | 2018-10-12 21:26:47.716 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
db_1        | 2018-10-12 21:26:47.716 UTC [1] LOG:  listening on IPv6 address "::", port 5432
db_1        | 2018-10-12 21:26:47.736 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db_1        | 2018-10-12 21:26:47.827 UTC [21] LOG:  database system was shut down at 2018-10-12 21:11:42 UTC
db_1        | 2018-10-12 21:26:47.845 UTC [1] LOG:  database system is ready to accept connections
composer_1  | Loading composer repositories with package information
composer_1  | Updating dependencies (including require-dev)
composer_1  | Your requirements could not be resolved to an installable set of packages.
composer_1  | 
composer_1  |   Problem 1
composer_1  |     - gumlet/php-image-resize 1.9.1 requires ext-gd * -> the requested PHP extension gd is missing from your system.
composer_1  |     - gumlet/php-image-resize 1.9.0 requires ext-gd * -> the requested PHP extension gd is missing from your system.
composer_1  |     - Installation request for gumlet/php-image-resize 1.9.* -> satisfiable by gumlet/php-image-resize[1.9.0, 1.9.1].
composer_1  | 
composer_1  |   To enable extensions, verify that they are enabled in your .ini files:
composer_1  |     - 
composer_1  |     - /usr/local/etc/php/conf.d/date_timezone.ini
composer_1  |     - /usr/local/etc/php/conf.d/docker-php-ext-sodium.ini
composer_1  |     - /usr/local/etc/php/conf.d/docker-php-ext-zip.ini
composer_1  |     - /usr/local/etc/php/conf.d/memory-limit.ini
composer_1  |   You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.
test_app_composer_1 exited with code 2

或者，您可以通过--ignore-platform-reqs and --no-scripts标记为install or update（如上所述here).

docker run --rm --interactive --tty \
    --volume $PWD:/app \
    composer install --ignore-platform-reqs --no-scripts

但我总是更喜欢在我的 php 容器中安装作曲家。