Containerization with Docker and PHP

Example Code

// To set up this example, create the following file structure:
// my-php-app/
// ├── docker-compose.yml
// ├── Dockerfile
// ├── nginx/
// │   └── default.conf
// └── src/
//     └── index.php

// --- File: docker-compose.yml ---
// This file defines the services for your multi-container PHP application.
version: '3.8'
services:
  web:
    image: nginx:alpine # Use a lightweight Nginx image
    ports:
      - "80:80" # Map host port 80 to container port 80
    volumes:
      - ./src:/var/www/html # Mount your application code into Nginx's document root
      - ./nginx/default.conf:/etc/nginx/conf.d/default.conf # Mount custom Nginx config
    depends_on:
      - app # Ensure the 'app' service starts before 'web'

  app:
    build:
      context: . # Look for Dockerfile in the current directory
      dockerfile: Dockerfile
    volumes:
      - ./src:/var/www/html # Mount your application code into PHP-FPM's working directory
    environment:
      # Environment variables for PHP application to connect to the database
      DATABASE_HOST: db
      DATABASE_USER: user
      DATABASE_PASSWORD: password
      DATABASE_NAME: my_database

  db:
    image: mysql:8.0 # Use MySQL 8.0 image
    environment:
      MYSQL_ROOT_PASSWORD: root_password
      MYSQL_DATABASE: my_database
      MYSQL_USER: user
      MYSQL_PASSWORD: password
    volumes:
      - db_data:/var/lib/mysql # Persist database data in a named volume

volumes:
  db_data: # Define the named volume for database persistence

# --- File: Dockerfile ---
# This Dockerfile builds the PHP-FPM application image.
FROM php:8.2-fpm-alpine # Start with a lightweight PHP-FPM base image (PHP 8.2)

# Install system dependencies and PHP extensions
RUN apk add --no-cache \ 
    nginx \ # Nginx is not strictly needed here if we use a separate Nginx container, but can be useful for debugging or single-container apps
    mysql-client \ # For connecting to MySQL from the PHP container
    git \ 
    build-base \ 
    autoconf \ 
    libtool \ 
    && docker-php-ext-install pdo_mysql opcache \ # Install PDO MySQL and Opcache extensions
    && docker-php-ext-enable opcache # Enable Opcache

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

# Copy application code from 'src/' directory to the container's working directory
# NOTE: In docker-compose, we use a volume mount for development, so this COPY might be skipped in some workflows
# For production images, you would copy the code here.
# COPY src/ .

# Expose port 9000 for PHP-FPM (the Nginx container will connect to this port)
EXPOSE 9000

# Command to run PHP-FPM when the container starts
CMD ["php-fpm"]

# --- File: nginx/default.conf ---
# Nginx configuration to proxy PHP requests to PHP-FPM.
server {
    listen 80;
    index index.php index.html;
    root /var/www/html; # Nginx serves files from this directory

    # Try to serve files directly, otherwise pass to index.php
    location / {
        try_files $uri $uri/ /index.php?$query_string;
    }

    # Pass PHP scripts to PHP-FPM
    location ~ \.php$ {
        try_files $uri =404; # Return 404 if PHP file not found
        fastcgi_split_path_info ^(.+\.php)(/.+)$; # Split URI into script name and path info
        fastcgi_pass app:9000; # Forward requests to the 'app' service (PHP-FPM) on port 9000
        fastcgi_index index.php;
        include fastcgi_params; # Include standard FastCGI parameters
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param PATH_INFO $fastcgi_path_info;
    }
}

# --- File: src/index.php ---
<?php
// Simple PHP application to demonstrate containerization

echo "<h1>Hello from a Dockerized PHP Application!</h1>";
echo "<p>This page is served by Nginx and processed by PHP-FPM running inside Docker containers.</p>";

// Optional: Try to connect to the database
$host = getenv('DATABASE_HOST') ?: 'db';
$user = getenv('DATABASE_USER') ?: 'user';
$password = getenv('DATABASE_PASSWORD') ?: 'password';
$dbname = getenv('DATABASE_NAME') ?: 'my_database';

try {
    $dsn = "mysql:host=$host;dbname=$dbname;charset=utf8mb4";
    $pdo = new PDO($dsn, $user, $password);
    $pdo->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
    echo "<p style='color: green;'>Successfully connected to the database!</p>";

    // Example: Create a simple table and insert data if not exists
    $pdo->exec("CREATE TABLE IF NOT EXISTS messages (id INT AUTO_INCREMENT PRIMARY KEY, message VARCHAR(255))");
    $stmt = $pdo->prepare("SELECT COUNT(*) FROM messages WHERE message = ?");
    $stmt->execute(['Hello Docker!']);
    if ($stmt->fetchColumn() == 0) {
        $pdo->exec("INSERT INTO messages (message) VALUES ('Hello Docker!')");
        echo "<p>Inserted 'Hello Docker!' into messages table.</p>";
    }

    // Retrieve and display messages
    $stmt = $pdo->query("SELECT message FROM messages");
    echo "<h2>Messages from DB:</h2><ul>";
    while ($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
        echo "<li>" . htmlspecialchars($row['message']) . "</li>";
    }
    echo "</ul>";

} catch (PDOException $e) {
    echo "<p style='color: red;'>Could not connect to the database: " . htmlspecialchars($e->getMessage()) . "</p>";
    echo "<p>Please ensure the 'db' service is running correctly and credentials are correct.</p>";
}

echo "<h2>PHP Info:</h2>";
phpinfo();
?>

// To run this example:
// 1. Save the files as described above.
// 2. Navigate to the 'my-php-app' directory in your terminal.
// 3. Run: `docker-compose up --build -d`
// 4. Open your browser and go to `http://localhost`
// 5. To stop and remove containers, networks, and volumes: `docker-compose down -v`