How to use Docker to work locally on WordPress websites with different PHP versions in MacOS

This article will help you to use Docker mainly for local development.

Maybe you are handling a WordPress website all by yourself, and don’t have a staging website to try all sorts of updates and plugins. This could be a great, easy and free alternative.

Download Docker

First of all, you need to download Docker Desktop, which will come with a fresh installation of Docker as well as a great UI to keep track of things without having to use too much command lines. But as we will need some, you can prepare yourself by opening the terminal, either by querying terminal.app in the search bar or from the launchpad.

Download Docker Desktop

When this is all set up, you can check that Docker is installed with this command line :

docker --version

You will get something like this :

Docker version 20.10.12, build e91ed57

Get a copy of your website

Before configuring Docker, you need to get a copy of your website on your computer.

• The entire sources
• An export of the database

This is the part where you might ask your web hoster to do this for you, or maybe use one WordPress plugin to create backup, I won’t focus on this.

Configure Docker for your local website

First of all, you need to create a new file to your WordPress repository.

This file will be at the root of the folder and named : docker-compose.yml

Basically, this file is used to create a container which will put different services and volumes together, in this particular case we need WordPress and MySQL.

WordPress will be fetch using an official image, it means it will execute some code on the container that was created by WordPress itself. Thanks to that, our job gets much easier because it already comes with everything that WordPress needs to work, including PHP.

MySQL is also an image, but as we need its data to be persisting we’ll put it in a volume. This is the purpose of a database, but volumes can be used for other things, for example logs.

Let’s that a closer look at everything that will be in the file :

version: "3.8"

This is the version of the Compose file, we will not mess with this and just get the latest as of March 2022 : https://docs.docker.com/compose/compose-file/compose-versioning/

services:
    wordpress:
        container_name: my-website
        image: wordpress
        restart: always
        ports:
          - 8001:80
        environment:
          WORDPRESS_DB_HOST: db
          WORDPRESS_DB_USER: my-user
          WORDPRESS_DB_PASSWORD: my-password
          WORDPRESS_DB_NAME: my-website
        volumes:
          - ./:/var/www/html

• container_name : if you do not name you container_name, it will be randomize. But this is useful to find in the desktop app or to target it from command lines.
• image : a lot of official images can be found on the Docker Hub like WordPress :https://hub.docker.com/_/wordpress
• restart : just making sure the container stays up in an error comes.
• ports : here you just bind the client host (80) to your own host (8001), this means your website will be on at http://localhost:8001
• environment: here you can set some global variables that can be useful, for instance we set everything related to our database, but as it’s also set in the wp-config.php file, I’d say it’s not that important. Just keep in mind the database host because it’s particular. The full list of available environments can be found on the image on Docker Hub.
• volumes : this indicate that the sources are in the current folder (./), and Docker maps this with its path /var/www/html, so that our sources are used for the container.

 db:
    container_name: db-wp
    image: mysql:5.7
    ports:
    - 3307:3306
    restart: always
    environment:
      MYSQL_DATABASE: my-website
      MYSQL_USER: my-user
      MYSQL_PASSWORD: my-password
      MYSQL_RANDOM_ROOT_PASSWORD: '1'
    volumes:
      - db:/var/lib/mysql

• image : Official image for MySQL 5.7, amongst other that you can find here : https://hub.docker.com/_/mysql. Also, if your database isn’t in MySQL, this is doable with other database management systems like MariaDB, Postgre...
• ports: you don’t actually need to specify this, the database will be created and stored, but I personally choose to show the port so that I can connect to it using TablePlus.
• environment : same as WordPress but with specific environments for MySQL
• volumes : again, this maps our own database with the one from the WordPress image.

You also need to set the volumes outside the services :

volumes:
  db:

Remember the database host “db” ? Here it is. We just named it. Now we can use it in wp-config.php and Docker will resolve it with an IP address.

That being said, this is what our file looks like with everything we discussed :

/docker-compose.yml

version: "3.8"

services:
  wordpress:
    container_name: my-website
    image: wordpress
    restart: always
    ports:
      - 8001:80
    volumes:
      - ./:/var/www/html
 db:
    container_name: db-wp
    image: mysql:5.7
    ports:
    - 3307:3306
    restart: always
    environment:
      MYSQL_DATABASE: exampledb
      MYSQL_USER: exampleuser
      MYSQL_PASSWORD: examplepass
      MYSQL_RANDOM_ROOT_PASSWORD: '1'
    volumes:
      - db:/var/lib/mysql

volumes:
  db:

Now, our website is ready.

The last step is to launch everything, so that Docker builds the local website. You need to go to the root of your website from the terminal, probably something like that :

cd /Users/me/my-website

And then the final command which will mount everything :

docker-compose up --build

The website can be accessed from a browser at http://localhost:8001 (or any port you mentioned)

Now let’s get a little bit further.

WordPress is written in PHP. It comes in many versions, you might not have the latest installed and want precisely to test an update. Same goes for MySQL even if it’s less often.

WordPress official Docker images allow us to mess with the versions.

You can try the following images to alter the PHP version :

• wordpress:php7.4-fpm
• wordpress:php7.3
• wordpress:php7.2
• wordpress:php7.1
• wordpress:php7.0
• wordpress:php5.6

To end this, just know that we can do anything with Docker. That includes starting from scratch and recreating the WordPress image, but that requires a lot of stuff that comes prebuilt here, like a nginx or Apache server, many PHP extensions... If we can, let's stick with official images.

This article is an extend to this introduction, published on the website of my agency (French) : https://www.pix-associates.com/blog/docker-definition-et-usages-on-vous-en-dit-plus