When running a PHP application, you almost always want to keep some environmentally dependent variables stored outside of your codebase. For example, it’s not a good idea to hard-code your database connection information because then you will have to remember to switch between local and production details while running your app. That’s a sure-fire way to screw something up.
There are a few ways to handle environmental variables in PHP when running
Docker containers, so in this post we’ll look at four options. For reference,
our PHP file (let’s call it
index.php) is going to be very simple, and just
output the value of a environmental variable called
<?php echo getenv('ENV_VAR');
Docker provides the
-e flag for passing environmental variables into any
container via the
docker run command. For example, we could run the PHP script
above with the following:
docker run --rm -v $(pwd):/app -w /app -e ENV_VAR='Hello World!' php:cli php index.php
Most of the options in this
docker run command are covered in the tutorial on
running PHP scripts within
but the last flag
-e ENV_VAR='Hello World!' sets a container-wide variable
that the PHP script can access, and you should see
Hello World! in the command
line when running this.
If you have a lot of environmental variables, it may make sense to put them into an environmental variables file. Docker can load all the variables from the file by passing in the filename like this:
docker run --rm -v $(pwd):/app -w /app --env-file .env php:cli php index.php
.env file should have at least this line:
Another way to include environmental variables is to include them in your
Dockerfile. This may not be good for variables you want to keep secret as
they’re going to be accessible by anyone with the built image you distribute,
but sometimes they make it easier when you want to use some values for
production and others for dev environments. First, we need to create a
Dockerfile for this project:
FROM php:cli ENV ENV_VAR='Hello World!'
And now we need to build this image:
docker build . -t envtest
Finally we can run the container using the new image we just created:
docker run --rm -v $(pwd):/app -w /app envtest php index.php
The last option we’ll cover works well if you’re using a hybrid Docker approach.
If some of your devs or servers are using Docker and others are not, you can
.env file in a volume and load it with the PHP Dotenv
package. You’ll need to install the
package first, and modify your PHP script a little.
docker run --rm -v $(pwd):/app composer/composer:latest require vlucas/phpdotenv
Next, update your PHP script to load the package:
<?php require('vendor/autoload.php'); $dotenv = new Dotenv\Dotenv( ); $dotenv->load(); echo getenv('ENV_VAR');
You’ll also need to make sure your
.env file uses quotes around any values
And then you can run the PHP script using your Docker command as we did in the previous tutorial:
docker run --rm -v $(pwd):/app -w /app php:cli php index.php
Now you have multiple options for loading environmental variables in PHP using Docker containers.
In this book, PHP developers will learn everything they need to know to start building their applications on Docker, including:
You can buy this book on Leanpub or sign up for my mailing list to get a coupon code to download it for FREE.