In this blog post, we will walk through how to Dockerize a CodeIgniter 3 application. By the end of this guide, you'll have a containerized application running with Apache, PHP, and MySQL, all managed via Docker Compose. This approach will streamline your development environment and ensure consistent setups across multiple systems.

Prerequisites

Before we dive into the details, make sure you have the following tools installed:

• Docker: To containerize the application and its dependencies.
• Docker Compose: To manage multi-container Docker applications.
• CodeIgniter 3: Your existing CodeIgniter 3 project.

Step 1: Setting Up Dockerfile:

The Dockerfile defines the environment in which your application will run. Here’s how to set it up:

# Use an official PHP image with Apache
FROM php:8.2-apache

# Enable Apache mod_rewrite for CodeIgniter
RUN a2enmod rewrite

# Set the working directory in the container
WORKDIR /var/www/html

# Copy project files into the container
COPY . /var/www/html

# Install necessary PHP extensions
RUN docker-php-ext-install mysqli

# Set proper permissions for Apache to access files
RUN chown -R www-data:www-data /var/www/html && chmod -R 755 /var/www/html

# Expose port 80
EXPOSE 80

Step 2: Setting Up Docker Compose

Now let’s define a docker-compose.yml file, which will configure and run multiple containers for both your web application and the database.

version: '3.8'

services:
  app:
    build:
      context: .
      dockerfile: Dockerfile
    container_name: ci3-docker  # Set the container name here
    ports:
      - "8080:80"  # Map port 80 of the container to port 8080 on the host
    volumes:
      - .:/var/www/html  # Mount current directory to /var/www/html inside the container
    depends_on:
      - db  # Ensure the database is up before starting the application

  db:
    image: mysql:8.0  # Uses the official MySQL image
    container_name: mysql
    restart: always
    environment:
      MYSQL_ROOT_PASSWORD: root  # Root password for MySQL
      MYSQL_DATABASE: ci3docker  # Initial database to create
    ports:
      - "3306:3306"  # Expose port 3306 for database connections
    volumes:
      - db_data:/var/lib/mysql  # Persist MySQL data

volumes:
  db_data:
    name: ci3-docker  # Name the volume for MySQL data persistence

Step 3: Build and Run the Containers

Once your Dockerfile and docker-compose.yml files are ready, it’s time to build and run the containers. In your project root, open a terminal and run the following commands:
Build the Docker images:

docker-compose build

Start the containers:

docker-compose up

This will start both the CodeIgniter application and the MySQL database. The app container will be accessible at http://localhost:8080, while the MySQL database will run on port 3306.

Step 4: Update CodeIgniter Database Configuration

Now, let’s ensure that CodeIgniter can connect to the MySQL database inside the container. Open your application/config/database.php and update the database connection settings:

$db['default'] = array(
    'dsn'   => '',
    'hostname' => 'db',  // Service name from Docker Compose
    'username' => 'root',
    'password' => 'root',  // Password set in docker-compose.yml
    'database' => 'ci3docker',  // Database name set in docker-compose.yml
    'dbdriver' => 'mysqli',
    'dbprefix' => '',
    'pconnect' => FALSE,
    'db_debug' => (ENVIRONMENT !== 'production'),
    'cache_on' => FALSE,
    'cachedir' => '',
    'char_set' => 'utf8',
    'dbcollat' => 'utf8_general_ci',
    'swap_pre' => '',
    'encrypt' => FALSE,
    'compress' => FALSE,
    'stricton' => FALSE,
    'failover' => array(),
    'save_queries' => TRUE
);

Step 5: Access the Application

Once the containers are up, visit http://localhost:8080 in your web browser. If everything is set up correctly, your CodeIgniter 3 application should be running smoothly inside a Docker container.

Step 6: Managing Docker Containers

To stop the containers, run:

docker-compose down

Conclusion

In this guide, we successfully Dockerized a CodeIgniter 3 application, making it portable and easy to manage. Docker Compose allows us to define and run multi-container applications with ease, making it perfect for development and production environments.

By using Docker, you ensure a consistent environment for all developers and easily deploy your application to various systems without worrying about dependencies. If you’re looking to scale your application or run it in a cloud environment, Docker makes it incredibly simple to manage.

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