PHP-FPM with Nginx

Quick Start

1. Run docker-compose up
2. Visit http://localhost/ in your browser.

Description

PHP is a popular programming language for web projects. It is usually run behind a webserver (like Apache or Nginx) to serve web traffic, API requests, etc.

This example is straightforward, running PHP-FPM behind a plain Nginx container, and Nginx routes requests to a PHP script that prints the environment information on a webpage. To set this up, we will run three containers:

1. Source code container (a data container to mount the source code we're running).
2. PHP container
3. Nginx container

We'll use docker-compose to orchestrate multiple containers on our host; see notes elsewhere in this repository for more information about docker-compose. There are a couple other unique things being done in the Nginx container's Dockerfile which are detailed below.

Installing Packages

In order to run a health check (see the next section) to determine if Nginx is running properly, we need to install curl, a command line utility to make HTTP requests, inside the container.

Because the upstream nginx:latest container uses Debian Jessie as a base image, we can easily install curl via apt-get. But to keep our Docker image more compact and efficient, we also need to clean up apt resources after the installation.

You might think to do this in a few steps, e.g.:

RUN apt-get update
RUN apt-get install -y curl
RUN rm -rf /var/lib/apt/lists/* && rm -Rf /usr/share/doc && rm -Rf /usr/share/man
RUN apt-get clean

However, if you do it this way, Docker will save not one but four extra image layers, taking up more space on your host, and slightly more time to build. Instead, it's recommended to do operations like installing new software in one giant RUN command, e.g.:

RUN apt-get update \
    && apt-get install -y curl \
    && rm -rf /var/lib/apt/lists/* \
    && rm -Rf /usr/share/doc && rm -Rf /usr/share/man \
    && apt-get clean

This way, when we build the Docker image via docker-compose, the curl installation will only add one layer, which is more efficient.

Health Check

One feature that can be useful in certain situations is Docker's built-in HEALTHCHECK functionality. In the nginx container's Dockerfile, there's a line that provides a command Docker can use to check whether the container is healthy:

HEALTHCHECK CMD curl --fail http://localhost/ || exit 1

Since we installed curl previously, we can use it to fetch localhost. If the request fails, curl will exit with an error, and Docker can use this to indicate whether the container is healthy or unhealthy while it's running.

You can check the status (after docker-compose up) using docker ps, or individually for this container with docker inspect [container_id]. Docker will provide one of the following statuses:

• starting
• healthy
• unhealthy

Note that if you want to disable a base image's HEALTHCHECK, you can add a line HEALTHCHECK NONE in your Dockerfile. There are also more options available to control the HEALTHCHECK interval, timeout, and retries. Read more about HEALTHCHECK in Docker's documentation.