Running a PHP Script in a Docker Container

If you’re used to running PHP command line applications, adding Docker could be a great way to increase the reusability and portability of your scripts. Docker allows you to run your code in isolated containers rather than on the host machine directly, meaning that even if you don’t have the same version of PHP or extensions installed, you can be sure that your script will run the same way on anyone’s Docker container anyway.

*Before we start, you should be familiar with writing command line scripts in PHP and you should have Docker installed.

Our PHP script

First, let’s look at a simple “Hello World” PHP script:

hello.php

<?php

$text = "Hello World!";

echo $text;

Now, open up a terminal and navigate to the directory where you saved . Let’s run that script within a Docker container using the latest version of PHP’s official CLI container:

$ docker run --rm -v $(pwd):/app -w /app php:cli php hello.php

When run, you should see the PHP CLI container being downloaded (the first time), then you should see the output Hello World!. You’ve just run a PHP script in Docker!

But what does it mean?

Let’s go over that Docker command (docker run...) and see what is going on:

• docker run This is Docker’s command to run a command within a new container. There are a lot of options that you can pass in, but I tried to keep them pretty minimal for this example.
• --rm This tells Docker to “remove” the container after the command is run. Alternatively, you can save the container and name it to run it again.
• -v $(pwd):/app This is telling Docker to mount a volume. You typically pass in a path to a folder on your root directory, a colon, and then a path to the folder in the container. Volumes are a powerful tool, but for this simple example we’re just mounting the current directory from our terminal into the /app directory in the new Docker container.
• -w /app This defines the Docker container’s “working directory.” That’s the place where it will look for code when you pass in a command to execute. Since we’re mounting our code into we obviously want Docker to run code from that directory.
• php:cli The first three items in this list were Docker run flags, but php:cli is the actual image we’re using for this container. There are other PHP containers on Docker Hub, so be sure to check them out if you’re doing something different like a web app or Apache server.
• php hello.php Finally, this is the actual command that we want to run on the container. It is run relative to the working directory we defined above.

You may think that was a long command to write just to run a PHP script, but think about what you didn’t have to do. You didn’t have to install PHP on your machine, and you could run that command in different versions of PHP by tweaking the php:cli parameter.

As you can see, it’s easy to run a PHP script within a Docker container. Docker might not be right for every project and workflow, but if portability and modularity are concerns, I’d highly recommend giving it a try.

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