Composer in php-fpm docker from composer:1.8.4 - php

Question

I have a .dockerfile that builds a php-fpm image and I try to install composer from a docker image like so:
FROM php:7.3.3-fpm-alpine as base
WORKDIR /var/www
# Override Docker configuration: listen on Unix socket instead of TCP
RUN sed -i "s|listen = 9000|listen = /var/run/php/fpm.sock\nlisten.mode = 0666|" /usr/local/etc/php-fpm.d/zz-docker.conf
# Install dependencies
RUN set -xe \
&& apk add --no-cache bash icu-dev \
&& docker-php-ext-install pdo pdo_mysql intl pcntl
CMD ["php-fpm"]
FROM composer:1.8.4 as composer
RUN rm -rf /var/www && mkdir /var/www
WORKDIR /var/www
COPY composer.* /var/www/
ARG APP_ENV=dev
RUN set -xe \
&& if [ "$APP_ENV" = "prod" ]; then export ARGS="--no-dev"; fi \
&& composer install --prefer-dist --no-scripts --no-progress --no-suggesthere
The problem is that the COPY composer.* /var/www/ does not seem to work properly because it throws the error:
composer install --prefer-dist --no-scripts --no-progress --no-suggest --no-interaction --no-dev
Composer could not find a composer.json file in /var/www
It seems like either the composer image is missing something or I skip some step, could you please assist, I am both new to docker and php.

Answer 1

Problem in the
WORKDIR /var/www
The WORKDIR command is used to define the working directory of a Docker container at any given time. The command is specified in the Dockerfile.
Any RUN, CMD, ADD, COPY, or ENTRYPOINT command will be executed in the
specified working directory.
Source: https://www.educative.io/edpresso/what-is-the-workdir-command-in-docker