How to work with docker and apache?

Question

PHP

The question arose that you need to deal with apache, php and docker to the heap. None of this has been touched before. Launched Docker, installed apache, php, mysql image, nginx has yet to be installed. But I fundamentally can not understand how to work with them now. How to change apache config? Why doesn't apache respond to the index.php file in volumes? Below is the docker-compose file I found on the internet. Can someone describe in general the procedure, at least approximately? Thank you.
PS before that, I just put apache into the system, but deleted it, I don’t know how good it turned out.

version: "2"
services:
  php:
    build: 
      context: './php/'
      args:
       PHP_VERSION: ${PHP_VERSION}
    networks:
      - backend
    volumes:
      - ./public_html/:/var/www/html/
      - ./php/php.ini:/usr/local/etc/php/php.ini
    container_name: php
  apache:
    build:
      context: './apache/'
      args:
       APACHE_VERSION: ${APACHE_VERSION}
    depends_on:
      - php
      - mysql
    networks:
      - frontend
      - backend
    ports:
      - "80:80"
    volumes:
      - ./src:/var/www/html
    container_name: apache
  mysql:
    image: mysql:5.6.26
    networks:
      - backend
    environment:
      - MYSQL_ROOT_PASSWORD=rootpassword
    container_name: mysql
networks:
  frontend:
  backend: