Write a Dockerfile for a PHP/Laravel application

Q: How do I install PHP extensions in a Docker image?

Use the docker-php-ext-install helper that ships with the official PHP images, for example docker-php-ext-install pdo pdo_mysql. Some extensions also need system packages installed first via apt-get.

Q: Why install Composer dependencies before copying all the code?

For build caching. Copy composer.json/composer.lock and run composer install first, then copy the rest. That way the slow install layer stays cached when you change only application code.

What we're building

We'll package a PHP application into an image. Everything here uses instructions you already learned - FROM, WORKDIR, RUN, COPY, CMD - just applied to a real stack.

The PHP Dockerfile

In your PHP project's root, create a Dockerfile:

FROM php:8.4-cli

WORKDIR /app

RUN apt-get update && apt-get install -y \
    unzip libpq-dev \
    && docker-php-ext-install pdo pdo_mysql

COPY --from=composer:latest /usr/bin/composer /usr/bin/composer

COPY composer.json composer.lock ./
RUN composer install --no-scripts --no-interaction

COPY . .

CMD ["php", "artisan", "serve", "--host=0.0.0.0", "--port=8000"]

Let's walk through it with what you already know:

FROM php:8.4-cli - start from the official PHP 8.4 image.
WORKDIR /app - work inside /app.
RUN apt-get ... docker-php-ext-install pdo pdo_mysql - install the system packages and PHP database extensions the app needs. docker-php-ext-install is a helper that ships with the official PHP image.
COPY --from=composer:latest ... - grab the Composer tool from the official composer image. (You'll learn more about copying from another image in the multi-stage lesson - for now, this just gives us composer.)
COPY composer.json composer.lock ./ then RUN composer install - remember the caching lesson: we copy the dependency files and install before copying the rest of the code, so dependencies stay cached when only source files change.
COPY . . - copy the rest of the application.
CMD [...] - run Laravel's built-in server, bound to 0.0.0.0 so it's reachable from outside the container (binding to localhost inside a container would only reach the container itself).

A .dockerignore

Add a .dockerignore so local junk and secrets don't get copied in:

.git
vendor
node_modules
.env
storage/logs/*.log

This is the same idea from the .dockerignore lesson, tuned for a PHP project.

Next, we'll pair this app image with a database using Compose.

The extension mistake that wastes an afternoon

The error that eats the most time when dockerizing PHP is a missing extension. Your app boots, then dies with something like "could not find driver" - which really means the pdo_mysql extension isn't installed in the image. PHP images don't include every extension by default; you add them with docker-php-ext-install, as in the Dockerfile above. When a PHP app fails only inside Docker, a missing extension is the first thing to check.

FAQ

How do I install PHP extensions in a Docker image?

Use the docker-php-ext-install helper that ships with the official PHP images, for example docker-php-ext-install pdo pdo_mysql. Some extensions also need system packages installed first via apt-get.

Why do I get "could not find driver" in a Dockerized PHP app?

The database PHP extension is missing from the image. Install it in your Dockerfile - for MySQL that's docker-php-ext-install pdo_mysql - then rebuild.

Why install Composer dependencies before copying all the code?

For build caching. Copy composer.json/composer.lock and run composer install first, then copy the rest. That way the slow install layer stays cached when you change only application code.