Containerisation (Docker for PHP)

Also Known As

TL;DR

Explanation

Docker containers bundle PHP, extensions, nginx/FPM configuration, and application code into an immutable image. Benefits: environment parity (eliminates 'works on my machine'), fast deployment, horizontal scaling, and isolation. A PHP production Dockerfile typically: starts from php:8.3-fpm-alpine, installs required extensions with docker-php-ext-install, copies Composer dependencies, and sets non-root user. Multi-stage builds separate build dependencies from runtime — keeping production images lean. Docker Compose orchestrates local development with PHP-FPM, nginx, MySQL, and Redis containers. For production, containers run on Kubernetes, ECS, or similar orchestrators.

Diagram

flowchart TD
    subgraph Host OS
        KERN[Linux Kernel]
        subgraph Container A
            PHPFPM[PHP-FPM]
            APP[App Code]
        end
        subgraph Container B
            NGINX[nginx]
        end
        subgraph Container C
            MYSQL[MySQL]
        end
    end
    NGINX -->|FastCGI| PHPFPM
    PHPFPM --> MYSQL
    KERN -.->|namespaces + cgroups| PHPFPM & NGINX & MYSQL
style KERN fill:#6e40c9,color:#fff
style PHPFPM fill:#238636,color:#fff
style NGINX fill:#1f6feb,color:#fff
style MYSQL fill:#d29922,color:#fff

Common Misconception

Why It Matters

Common Mistakes

• Running containers as root inside the container — any container escape gives the attacker root on the host.
• Storing persistent data inside the container — it disappears when the container restarts.
• Using latest as the image tag in production — you lose control of which version is deployed.
• Baking secrets into the image — they are visible to anyone who can pull the image.

Code Examples

// Dockerfile anti-patterns:
FROM ubuntu:latest          # Unpinned — breaks on new release
RUN apt-get install -y php  # No version pin
COPY . /app                 # Copies .git, node_modules, .env
RUN composer install        # Dev dependencies included
USER root                   # Running as root — security risk

// Better:
FROM php:8.3-fpm-alpine
COPY --chown=www-data:www-data . /app
RUN composer install --no-dev --optimize-autoloader
USER www-data

# Dockerfile — production PHP-FPM image
FROM php:8.3-fpm-alpine AS base
RUN docker-php-ext-install pdo_mysql opcache
COPY php.ini /usr/local/etc/php/conf.d/app.ini

FROM base AS vendor
COPY composer.json composer.lock ./
RUN composer install --no-dev --no-scripts --prefer-dist

FROM base AS production
COPY --from=vendor /app/vendor ./vendor
COPY . .
RUN php artisan config:cache && php artisan route:cache
USER www-data

References

• ↗ https://docs.docker.com/language/php/
• ↗ https://hub.docker.com/_/php

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