Add documentation and examples

docs/composer-support.md

@@ -0,0 +1,35 @@
+# Adding composer
+
+If you need [Composer](https://getcomposer.org/) in your project, here's an easy way to add it.
+
+```Dockerfile
+FROM trafex/php-nginx:latest
+
+# Install composer from the official image
+COPY --from=composer /usr/bin/composer /usr/bin/composer
+
+# Run composer install to install the dependencies
+RUN composer install --optimize-autoloader --no-interaction --no-progress
+```
+
+## Building with composer
+
+If you are building an image with source code in it and dependencies managed by composer then the definition can be improved.
+The dependencies should be retrieved by the composer but the composer itself (`/usr/bin/composer`) is not necessary to be included in the image.
+
+```Dockerfile
+FROM composer AS composer
+
+# Copying the source directory and install the dependencies with composer
+COPY <your_directory>/ /app
+
+# Run composer install to install the dependencies
+RUN composer install \
+  --optimize-autoloader \
+  --no-interaction \
+  --no-progress
+
+# Continue stage build with the desired image and copy the source including the dependencies downloaded by composer
+FROM trafex/php-nginx:latest
+COPY --chown=nginx --from=composer /app /var/www/html
+```