How to change the document root in PHP:7.1-apache from docker-compose.yml

I found a solution for this issue. basically, it worked when I created a Dockerfile with build commands. So the following structure fixed the issue:

docker-compose.yml

version: '3'
services:
    web:
        build: .
        ports:
            - 80:80
        volumes:
            - ./src:/var/www/html

Dockerfile

FROM php:7.1-apache

ENV APACHE_DOCUMENT_ROOT=/var/www/html/public
RUN sed -ri -e 's!/var/www/html!${APACHE_DOCUMENT_ROOT}!g' /etc/apache2/sites-available/*.conf
RUN sed -ri -e 's!/var/www/!${APACHE_DOCUMENT_ROOT}!g' /etc/apache2/apache2.conf /etc/apache2/conf-available/*.conf

Just remember to run docker-compose build before running the image (if anybody else have the same problem).

For testing temporary solutions, you can manually change the apache .conf file. When your container is running, enter the bash:

docker exec -it your_container_name bash

Edit the content of the .conf file:

vim /etc/apache2/sites-available/000-default.conf

(if vim is not found, run apt-get update and apt-get install vim)

Finally reload apache:

/etc/init.d/apache2 reload