Dockerized example for article at Pehapkari.cz about running multiple PHP versions: https://pehapkari.cz/blog/2017/03/27/multiple-php-versions-the-easy-way/

Dockerfile

FROM debian:stretch

ENV DEBIAN_FRONTEND noninteractive

# install NGINX
RUN apt-get update && \
	apt-get install -y nginx --no-install-recommends && \
	rm -rf /var/lib/apt/lists/*


# install PHP 7.0
RUN apt-get update && \
	apt-get install -y php7.0-cli php7.0-fpm --no-install-recommends && \
	rm -rf /var/lib/apt/lists/*


# install PHP 5.6
RUN apt-get update && \
	apt-get install -y apt-transport-https ca-certificates curl gnupg --no-install-recommends && \
	rm -rf /var/lib/apt/*
RUN curl https://packages.sury.org/php/apt.gpg | apt-key add -
RUN echo 'deb https://packages.sury.org/php/ stretch main' > /etc/apt/sources.list.d/deb.sury.org.list
RUN apt-get update && \
	apt-get install -y php5.6-cli php5.6-fpm --no-install-recommends && \
	rm -rf /var/lib/apt/lists/*


# verify versions
RUN php7.0 -v
RUN php5.6 -v
RUN php -v


# clear active virtual hosts
RUN rm -f /etc/nginx/sites-enabled/*


# prepare PHP 7.0 virtual host
RUN mkdir /var/www/site-with-php7.0
COPY index.php /var/www/site-with-php7.0/index.php
COPY site-with-php7.0.vhost /etc/nginx/sites-available/site-with-php7.0


# prepare PHP 5.6 virtual host
RUN mkdir /var/www/site-with-php5.6
COPY index.php /var/www/site-with-php5.6/index.php
COPY site-with-php5.6.vhost /etc/nginx/sites-available/site-with-php5.6


# enable the virtual hosts
RUN ln -s ../sites-available/site-with-php5.6 /etc/nginx/sites-enabled
RUN ln -s ../sites-available/site-with-php7.0 /etc/nginx/sites-enabled


# (Docker-specific) install supervisor so we can run everything together
RUN apt-get update && \
	apt-get install -y supervisor --no-install-recommends && \
	rm -rf /var/lib/apt/lists/*
COPY supervisor.conf /etc/supervisor/supervisord.conf
RUN mkdir /run/php

EXPOSE 8870 8856
CMD ["supervisord", "-c", "/etc/supervisor/supervisord.conf"]

index.php

<?php
phpinfo();

site-with-php5.6.vhost

server {
    listen 8856 default_server;
    listen [::]:8856 default_server;
    server_name _;
    root /var/www/site-with-php5.6;
    index index.php;
    location / {
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/run/php/php5.6-fpm.sock; # adjust for the listen setting discussed above
    }
}

site-with-php7.0.vhost

server {
    listen 8870 default_server;
    listen [::]:8870 default_server;
    server_name _;
    root /var/www/site-with-php7.0;
    index index.php;
    location / {
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/run/php/php7.0-fpm.sock; # adjust for the listen setting discussed above
    }
}

supervisor.conf

[supervisord]
nodaemon = true

[program:php70]
command = php-fpm7.0 -F -y /etc/php/7.0/fpm/php-fpm.conf
user = root
autostart = true

[program:php56]
command = php-fpm5.6 -F -y /etc/php/5.6/fpm/php-fpm.conf
user = root
autostart = true

[program:nginx]
command = /usr/sbin/nginx -g 'daemon off;'
user = root
autostart = true

try-me.sh

#!/bin/bash

docker build -t multiphp .
docker run --rm -P multiphp