In the `Dockerfile`, you'll need to update the following:

1. Split the `deps` staged into two stages. One stage for production
   (`prod-deps`) and one stage (`dev-deps`) to install development dependencies.
2. Create a common `base` stage.
3. Create a new `development` stage for development.
4. Update the `final` stage to copy dependencies from the new `prod-deps` stage.

The following is the `Dockerfile` before and after the changes.

{{< tabs >}}
{{< tab name="Before" >}}

```dockerfile
# syntax=docker/dockerfile:1

FROM composer:lts as deps
WORKDIR /app
RUN --mount=type=bind,source=composer.json,target=composer.json \
    --mount=type=bind,source=composer.lock,target=composer.lock \
    --mount=type=cache,target=/tmp/cache \
    composer install --no-dev --no-interaction

FROM php:8.2-apache as final
RUN docker-php-ext-install pdo pdo_mysql
RUN mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"
COPY --from=deps app/vendor/ /var/www/html/vendor
COPY ./src /var/www/html
USER www-data
```

{{< /tab >}}
{{< tab name="After" >}}

```dockerfile
# syntax=docker/dockerfile:1

FROM composer:lts as prod-deps
WORKDIR /app
RUN --mount=type=bind,source=./composer.json,target=composer.json \
    --mount=type=bind,source=./composer.lock,target=composer.lock \
    --mount=type=cache,target=/tmp/cache \
    composer install --no-dev --no-interaction

FROM composer:lts as dev-deps
WORKDIR /app
RUN --mount=type=bind,source=./composer.json,target=composer.json \
    --mount=type=bind,source=./composer.lock,target=composer.lock \
    --mount=type=cache,target=/tmp/cache \
    composer install --no-interaction

FROM php:8.2-apache as base
RUN docker-php-ext-install pdo pdo_mysql
COPY ./src /var/www/html

FROM base as development
COPY ./tests /var/www/html/tests
RUN mv "$PHP_INI_DIR/php.ini-development" "$PHP_INI_DIR/php.ini"
COPY --from=dev-deps app/vendor/ /var/www/html/vendor

FROM base as final
RUN mv "$PHP_INI_DIR/php.ini-production" "$PHP_INI_DIR/php.ini"
COPY --from=prod-deps app/vendor/ /var/www/html/vendor
USER www-data
```

{{< /tab >}}
{{< /tabs >}}

Update your `compose.yaml` file by adding an instruction to target the
development stage.

The following is the updated section of the `compose.yaml` file.

```yaml {hl_lines=5}
services:
  server:
    build:
      context: .
      target: development
      # ...
```

Your containerized application will now install the dev dependencies.

Run the following command to start your application.

```console
$ docker compose up --build
```

Open a browser and view the application at [http://localhost:9000/hello.php](http://localhost:9000/hello.php). You should still see the simple "Hello, Docker!" application.

Press `ctrl+c` in the terminal to stop your application.

While the application appears the same, you can now make use of the dev dependencies. Continue to the next section to learn how you can run tests using Docker.

## Summary

In this section, you took a look at setting up your Compose file to add a local
database and persist data. You also learned how to use Compose Watch to automatically sync your application when you update your code. And finally, you learned how to create a development container that contains the dependencies needed for development.

Related information:

- [Compose file reference](/reference/compose-file/)
- [Compose file watch](/manuals/compose/how-tos/file-watch.md)
- [Dockerfile reference](/reference/dockerfile.md)
- [Official Docker Image for PHP](https://hub.docker.com/_/php)

## Next steps

In the next section, you'll learn how to run unit tests using Docker.