Docker Book

Notes for upcoming book on Docker and PHP.

Installing Docker

• Point to instructions on Docker website, no point in duplicating these
• Make sure you are running the latest version
• Use upstream repositories as the distribution ones are too out of date
• If running Ubuntu, use LTS as the host

Hello World

• docker run --rm hello-world
• Include example output for checking
• Explain use of --rm flag - without this we end up with lots of stopped but not removed images

Basic PHP example

• docker run --rm php:7.4-apache-buster php -v, show output

Dockerfile:

 FROM php:7.4-apache-buster
 COPY index.php /var/www/html/index.php

index.php:

 <?php phpinfo();

• docker build -t phpinfo:latest .
• docker run --rm -p 8000:80 phpinfo
• Visit localhost:8000 in browser
• Ctrl+C terminates container and Docker will remove it automatically due to the --rm flag

Docker Compose

Docker Composer (docker-compose) is a way to configure Docker with YAML. For example, you can specify environment variables in a YAML list, instead of having to supply them all on the command line. It also makes life much easier if you want to run multiple containers together, e.g. web and database containers.

If you are adding Docker to a project for the first time, you should use Docker Compose by default.

Dependencies

If you have multiple containers, it is likely that there will be dependencies between them. For example, the container hosting your web application most likely depends on the database container - until the database container has been started, the application is not 'ready'.

Dependencies can be expressed with the depends_on attribute.