Docker for PHP Development

# CHAPTER 10

Docker for PHP Development #

1. Introduction #

2. Learning Objectives #

• Identify the correct official PHP Docker image variants (CLI, FPM, Apache).

• Host a dynamic PHP application using Docker Compose.

• Install necessary PHP extensions (like mysqli or pdo) inside a custom Dockerfile.

• Understand the difference between PHP-Apache and Nginx + PHP-FPM architectures.

• Run Composer commands via Docker without installing Composer on your host machine.

3. Beginner-Friendly Explanation #

• The XAMPP Way: You permanently weld a set of metric wrenches to your hands. You can easily fix Japanese cars. But if an American car comes in requiring imperial wrenches, you cannot fix it. You have to undergo surgery to change your hands.

• The Docker Way: You have a closet full of mechanical robot suits. Suit 1 has metric tools (PHP 8.2). Suit 2 has imperial tools (PHP 7.4). When a car arrives, you step into the correct suit, fix the car, and step out. Your actual hands remain completely clean and unmodified.

4. The PHP Image Variants #

1. 1. php:8.2-cli: Just the raw PHP command-line interpreter. Used for running background scripts or Laravel Artisan commands. It cannot host a website.

1. 2. php:8.2-apache: An all-in-one image. It contains Apache web server and PHP bolted together. It is heavy, but incredibly easy for beginners. Just drop in your files and it works.

1. 3. php:8.2-fpm: (FastCGI Process Manager). The modern, high-performance standard. It contains ONLY PHP. It must be paired with a separate Nginx container acting as the web server to handle the HTTP requests.

5. Installing PHP Extensions #

*Example Dockerfile for a PHP Database App:*

FROM php:8.2-apache
# Install the MySQL PDO extension
RUN docker-php-ext-install pdo pdo_mysql
# Enable Apache mod_rewrite for modern routing
RUN a2enmod rewrite

6. Running Composer in Docker #

docker run --rm -v $(pwd):/app composer install

*What happens:* Docker spins up a temporary container containing Composer, mounts your local project folder into /app, downloads the packages into a new vendor folder on your laptop, and instantly deletes the Composer container!

7. Mini Project: Dockerize a Dynamic PHP App #

Step-by-Step Tutorial:

1. 1. Create a folder named php-docker-app. Open your terminal and cd into it.

1. 2. Create an index.php file:

<?php
$version = phpversion();
echo "<h1>Success! Running PHP Version: $version</h1>";
?>

1. 3. Create a docker-compose.yml file:

version: '3.8'
services:
  app:
    image: php:8.2-apache
    ports:
      - "8000:80"
    volumes:
      - ./:/var/www/html

1. 4. Run the stack:

docker-compose up -d

1. 5. Open your browser to http://localhost:8000. You will see PHP dynamically rendering the version!

1. 6. Because of the volume mount (./:/var/www/html), you can edit index.php, click save, and refresh the browser to see instant changes. No XAMPP required!

8. Real-World Scenarios #

9. Best Practices #

• Production Architecture (Nginx + FPM): While the php-apache image is fantastic for local development, professional enterprise deployments decouple the stack. They use a custom Nginx container to handle raw HTTP traffic and serve static images/CSS, and they route .php file requests over a private Docker network to a separate php-fpm container to crunch the dynamic code. This allows the Web Server and the PHP processor to scale independently.

10. Common Mistakes #

• Missing File Permissions: When running composer install via a Docker volume mount on Linux, the files downloaded into the vendor folder might be owned by the Docker root user. If you try to delete them using your normal Linux user account, you will get "Permission Denied" errors. You must configure user ID mapping or use sudo chown to reclaim ownership of your files.

11. Exercises #

1. 1. Explain the architectural difference between the php:8.2-apache image and the php:8.2-fpm image.

1. 2. What specific Dockerfile command is utilized to install missing database drivers into an official PHP image?

12. FAQs #

13. Interview Questions #

• Q: A developer complains that their newly containerized PHP application throws a "PDOException: could not find driver" error when attempting to connect to MySQL. Detail the exact steps required to resolve this issue utilizing a Dockerfile.

• Q: Describe the architectural advantages of utilizing an Nginx + PHP-FPM multi-container architecture in production versus deploying a monolithic Apache+PHP container.

14. Summary #

15. Next Chapter Recommendation #