Docker deployment in Laravel - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output when running Laravel inside Docker with this Dockerfile?

Consider this Dockerfile for a Laravel app. What will be the result when you build and run the container?

FROM php:8.1-fpm
WORKDIR /var/www/html
COPY . .
RUN docker-php-ext-install pdo pdo_mysql
CMD ["php-fpm"]

Laravel

FROM php:8.1-fpm
WORKDIR /var/www/html
COPY . .
RUN docker-php-ext-install pdo pdo_mysql
CMD ["php-fpm"]

A The container runs PHP-FPM serving the Laravel app, but no web server is included so no HTTP requests are handled.

B The container runs a full Apache server serving the Laravel app out of the box.

C The container fails to build because pdo_mysql extension is not available for PHP 8.1.

D The container runs but Laravel will not connect to the database because no database service is included.

💡 Hint

Think about what PHP-FPM does and what is missing to serve HTTP requests.

This Dockerfile uses the official PHP-FPM image which runs PHP FastCGI Process Manager. It does not include a web server like Apache or Nginx. So while PHP runs, HTTP requests won't be served unless a web server is added.

📝 Syntax

intermediate

Which docker-compose.yml snippet correctly defines a Laravel app with MySQL service?

You want to run Laravel with a MySQL database using Docker Compose. Which snippet is correct?

Laravel

version: '3.8'
services:
  app:
    build: .
    ports:
      - "8000:80"
    depends_on:
      - db
  db:
    image: mysql:8
    environment:
      MYSQL_ROOT_PASSWORD: secret
      MYSQL_DATABASE: laravel
      MYSQL_USER: user
      MYSQL_PASSWORD: secret

A The app service should expose port 3306 for MySQL, not 8000.

B The snippet is missing volumes for persistent MySQL data, so data will be lost on restart.

C The snippet is correct and will start Laravel app on port 8000 with MySQL database.

D The environment variables for MySQL are incorrect; MYSQL_USER is not valid.

💡 Hint

Check if the services and environment variables match Laravel and MySQL requirements.

This docker-compose.yml correctly defines an app service built from the current directory and a MySQL 8 service with proper environment variables. Port 8000 is mapped for the app HTTP traffic. Volumes are recommended but not required.

🔧 Debug

advanced

Why does Laravel fail to connect to MySQL in this Docker setup?

Given this docker-compose.yml snippet:

services:
  app:
    build: .
    environment:
      DB_HOST: localhost
      DB_DATABASE: laravel
      DB_USERNAME: user
      DB_PASSWORD: secret
  db:
    image: mysql:8
    environment:
      MYSQL_ROOT_PASSWORD: secret
      MYSQL_DATABASE: laravel
      MYSQL_USER: user
      MYSQL_PASSWORD: secret

Laravel inside the app container cannot connect to MySQL. Why?

Laravel

services:
  app:
    build: .
    environment:
      DB_HOST: localhost
      DB_DATABASE: laravel
      DB_USERNAME: user
      DB_PASSWORD: secret
  db:
    image: mysql:8
    environment:
      MYSQL_ROOT_PASSWORD: secret
      MYSQL_DATABASE: laravel
      MYSQL_USER: user
      MYSQL_PASSWORD: secret

A DB_HOST should be 'db' not 'localhost' because containers have separate networks.

B The MySQL image version 8 is incompatible with Laravel's database driver.

C The environment variables must be set in a .env file, not in docker-compose.yml.

D The app container needs to expose port 3306 to connect to MySQL.

💡 Hint

Think about how Docker containers communicate by service name, not localhost.

Inside Docker Compose, containers communicate using service names as hostnames. 'localhost' refers to the container itself, so Laravel cannot reach the MySQL container using 'localhost'. Using 'db' as DB_HOST fixes this.

❓ lifecycle

advanced

What happens if you run 'docker-compose down' in a Laravel Docker setup with volumes?

You have a Laravel app and MySQL running with Docker Compose. The MySQL service uses a named volume for data. What happens when you run 'docker-compose down'?

Laravel

version: '3.8'
services:
  app:
    build: .
  db:
    image: mysql:8
    volumes:
      - mysql_data:/var/lib/mysql
volumes:
  mysql_data:

A The command fails because volumes cannot be used with 'docker-compose down'.

B The containers and the MySQL data volume are deleted, losing all database data.

C Only the app container is removed; the db container and volume remain running.

D The containers stop and are removed, but the MySQL data volume remains intact.

💡 Hint

Consider the difference between 'docker-compose down' and 'docker-compose down -v'.

'docker-compose down' stops and removes containers and networks but preserves named volumes. To remove volumes, you must add the '-v' flag.

🧠 Conceptual

expert

Which is the best way to optimize Laravel Docker image size for production?

You want to deploy a Laravel app with Docker in production. Which approach best reduces the final image size while keeping functionality?

A Use a single Dockerfile with all build tools and runtime in one image to avoid complexity.

B Use a multi-stage Dockerfile: build assets and dependencies in one stage, then copy only needed files to a smaller PHP runtime image.

C Use the official php:8.1-fpm image and install all composer dependencies and node modules inside it directly.

D Use Alpine Linux base image and install all Laravel dependencies manually to minimize size.

💡 Hint

Think about separating build environment from runtime environment.

Multi-stage builds allow compiling and installing dependencies in a build stage, then copying only the necessary runtime files to a smaller base image. This reduces image size and attack surface.