Docker layer caching with php composer

Dockerfile

# create our app directory
RUN mkdir -p /var/www

# Set it as our working dir
WORKDIR /var/www

# add our composer dependancies
ADD composer.json ./

# install our dependancies without running scripts 
# then remove composers cache to save space
RUN composer install --no-scripts --no-autoloader --prefer-dist -vvv \
    && rm -rf /root/.composer/cache