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docker |
Docker - a lightweight alternative to a full virtual machine - is so called because it's all about "containers". A container is a building block which, in the simplest case, does one specific job, e.g. running a web server. An "image" is the package you use to build the container - Docker has a repository full of them.
A typical LAMP application might have three containers: a web server, a PHP-FPM process and MySQL. As with shared folders in Vagrant, you can leave your application files where they are and tell Docker where to find them.
You can generate containers from the command line (see example below) or, for ease of maintenance, build a docker-compose.yml file for your project specifying which to create and how they communicate with one another.
Docker may help if you're developing multiple websites and want the separation that comes from installing each on its own virtual machine, but don't have the necessary disk space or the time to keep everything up to date. It's efficient: the installation and downloads are quicker, you only need to store one copy of each image however often it's used, containers need less RAM and share the same OS kernel, so you can have more servers running simultaneously, and it takes a matter of seconds to stop and start them, no need to wait for a full server boot.
After installing docker on your machine, you can start a web server with one command.
The following will download a fully functional Apache installation with the latest PHP version, map /path/to/your/php/files to the document root, which you can view at http://localhost:8080:
{% highlight console %} docker run -d --name my-php-webserver -p 8080:80 -v /path/to/your/php/files:/var/www/html/ php:apache {% endhighlight %}
This will initialize and launch your container. -d makes it run in the background. To stop and start it, simply run docker stop my-php-webserver and docker start my-php-webserver (the other parameters are not needed again).
The command above shows a quick way to run a basic server. There's much more you can do (and thousands of pre-built images in the Docker Hub). Take time to learn the terminology and read the Docker User Guide to get the most from it, and don't run random code you've downloaded without checking it's safe – unofficial images may not have the latest security patches. If in doubt, stick to the official repositiories.
The PHPDocker.io site will auto-generate all the files you need for a fully-featured LAMP/LEMP stack, including your choice of PHP version and extensions.