Get PHP Composer to Run On Docker Container [A How To Guide]
Full stack web developer, tech lead, project manager
I have a php docker container, that runs my app, and I need to start using Composer to install a php package. What is the best way to approach it?
Source files can be found here:
1. Not the best approach, but the most straightforward one: not to use "php:7.2-fpm" image, but to build a custom image with both php and composer.
Technically this works, I get composer installed in my php image, and whenever I need to update or install dependencies I simply execute calls in my custom php container.
- need to use composer in several different containers - results in custom images for each container, where composer is needed
- if I run docker in swarm mode and scale container to more than 1 copy - results in each container executing "composer install"
2. A much better approach: use a dedicated composer docker image, map my project inside, and execute composer commands.
Create docker-compose.yml file in "docker" folder:
command: ["redis-server", "--appendonly", "yes"]
command: ["composer", "install"]
Here I do several things:
- /var/www/docker-study.loc/recipe-05/php:/app - composer image by default executes commands from /app folder, that's why I map project like this
- I map /var/www/docker-study.loc/recipe-05/php to both, php container and composer container, this way composer container can execute "composer install", and php container will have the updated code
- "depends_on" - prevents container to start before other container, on which it depends
3. Create composer.json in "php" folder:
4. Create index.php in "php" folder:
require __DIR__ . '/vendor/autoload.php';
$client = new Predis\Client([
'scheme' => 'tcp',
'host' => 'redis',
'port' => 6379,
$value = $client->get('foo');
The goal here is to use composer library - "predis/predis" (just as an example). This library needs to get installed once "composer" container gets started.
I can go to /var/www/docker-study.loc/recipe-05/docker/ and execute:
Now go to myapp.loc/ and see "works!"
5. Final Thoughts.
When composer container started, it executed "composer install" command and then exited. I can confirm this by running: "docker container ls -a" - this will show that container "docker_composer_1" has exited.
If I do - "docker logs docker_composer_1" - I can see information on what happened when container started, and how "composer install" process went.
What if I change composer.json file, and need to install additional library?
docker-compose restart composer
This will start this container again, execute install and exit.
What if I need to run "composer update" instead of "composer install"?
I can change "install" -> "update" in docker-compose.yml, and run "docker-compose restart composer"
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