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How to Use Docker to Containerise PHP and Apache

Docker containers make your app portable across environments. Once you’ve got a container image, you can use it anywhere Docker is available. Here’s how to containerise a PHP web application using the Apache server.

We’ll use the official PHP Docker image as our base. Variants preconfigured with Apache are provided, so you won’t need to install the web server yourself. The PHP base image also offers convenience utilities for managing PHP extensions.

Creating a Dockerfile

Docker images are created from a Dockerfile. This file contains instructions which are used to build the image. Instructions include COPY, to copy files and folders into the container, and RUN, which runs a command within the container.

You can get a simple PHP site running by simply copying its files into an image based on php:8.0-apache.

FROM php:8.0-apache
WORKDIR /var/www/html

COPY index.php index.php
COPY src/ src
EXPOSE 80
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This Dockerfile takes index.php and src from our working directory and copies them into the Apache document root. You could now build the image and start a container from it. You’d see your site being served by Apache.

docker build -t my-php-site:latest .
docker run -d -p 80:80 my-php-site:latest

The PHP Docker images have the Apache document root at the default Debian location of /var/www/html. The WORKDIR instruction in the Dockerfile means subsequent commands will be executed within the document root.

Apache exposes itself on the default web server port of 80. The EXPOSE directive in the Dockerfile indicates this. By explicitly exposing the port, you can use the -P flag with docker run to automatically bind a random host port to the container’s port 80.

Customising Apache Configuration

The official PHP/Apache images are based on Debian. You can use the apt package manager to add extra software you need.

You’ve also got full access to Apache’s built-in tools. You can use a2enmod/a2dismod to manage modules and a2ensite/a2dissite to interact with virtual hosts.

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The Apache configuration file defaults to /etc/apache2/apache2.conf. Add lines to this file, or replace it entirely, to extend the Apache configuration.

One change that’s always worth making is to explicitly set the Apache ServerName. This stops the “unable to reliably determine ServerName” warning which usually appears in your container’s logs.

You’ll also usually want to add your own Apache virtual host. This lets you set up custom configuration beyond what the Apache 000-default site provides. Here’s how to make those changes.

COPY my-apache-site.conf /etc/apache2/sites-available/my-apache-site.conf

RUN echo "ServerName localhost" >> /etc/apache2/apache2.conf &&\
    a2enmod rewrite &&\
    a2dissite 000-default &&\
    a2ensite my-apache-site &&\
    service apache2 restart

This example disables the default site, enables the custom site and restarts Apache to apply the changes. The mod_rewrite module is enabled too, enabling use of Rewrite directives in .htaccess files. You may want to enable other modules as well, such as headers if your configuration will interact with response headers.

Adding PHP Extensions

PHP Docker images come with extension management utilities built-in. Some extensions are enabled by default – you can check what’s available by running php -m within a running container.

Many common extensions can be installed using docker-php-ext-install:

docker-php-ext-install pdo_mysql
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Some extensions need to be configured before they can be installed. You can use docker-php-ext-configure to perform pre-install configuration. The available options will vary by extension. Read the extension’s manual page to determine the flags you can supply.

RUN docker-php-ext-configure gd --with-jpeg=/usr/include/ &&\
    docker-php-ext-install gd

You can also use extensions distributed via PECL. These extensions require a two-step installation procedure. Install the PECL package first, then use docker-php-ext-enable to register the extension with your PHP installation.

RUN apt-get install -y libmcached-dev zlib1g-dev &&\
    pecl install memcached-3.1.5 &&\
    docker-php-ext-enable memcached

PHP Configuration

The Docker images are preconfigured to load PHP configuration files found in /usr/local/etc/php/conf.d. Add your own .ini file to this directory. PHP will include its contents at runtime, overwriting any existing values. This is the recommended way to extend the default configuration.

The configuration directory path could change in the future. You can get its current location using the $PHP_INI_DIR environment variable. It currently resolves to /usr/local/etc/php/conf.d.

RELATED: How to Run GUI Applications in a Docker Container

Using Composer

Composer isn’t available by default. Composer is a community effort that exists independently of PHP. You need to manually install it if you want to use it in a Docker container.

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The best way of using Composer in your builds is to reference the tool’s own Docker image via a multi-stage build. Use COPY --from to bring the Composer binary into your PHP container; you can then use Composer as normal to install your project’s dependencies.

COPY --from=composer:2 /usr/bin/composer /usr/bin/composer
COPY composer.json composer.json
COPY composer.lock composer.lock
RUN composer install --no-dev

Using this approach reduces complexity. You don’t need to download and run the Composer installation script. By referencing composer:2, Docker will pull the image and then copy out the Composer binary.

Custom Entrypoint Scripts

You might need to use a custom entrypoint script if you want to run application migrations before the main server runtime starts. You can override the container ENTRYPOINT to use your own startup sequence.

You can make the container execution continue as normal by executing apache2-foreground. This will run Apache in the foreground, preventing the container from exiting after the entrypoint script completes.

ENTRYPOINT ["bash", "/Docker.sh"]

Docker.sh contents:

php app.php my-migration-command    # run migrations
service cron start                  # start some services
exec apache2-foreground             # main execution

RELATED: How to Install Docker and Docker Compose on Linux

Conclusion

Dockerising a PHP web service is straightforward when using the official images. You can readily configure Apache and PHP with extensions and your own configuration files.

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You’re most likely to encounter difficulties when trying to use third-party community addons like Composer. These aren’t included by default, so you’ll need to use multi-stage Docker builds or manual installation procedures.

Using Docker gives your application versatility in how and where it’s deployed. With your image, you can spin up a working installation of your site using only docker build and docker run in your terminal.

James Walker James Walker
James Walker is a contributor to CloudSavvy IT. He is the founder of Heron Web, a UK-based digital agency providing bespoke software development services to SMEs. He has experience managing complete end-to-end web development workflows, using technologies including Linux, GitLab, Docker, and Kubernetes. Read Full Bio »


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