This is an example Dockerfile that shows how to run a Docker container with the PHP built-in webserver.
Read more about it: http://php.net/manual/en/features.commandline.webserver.php
docker run -p 8080:8080 -it karelbemelmans/php-simple
And then browse to http://localhost:8080/php.php to test it.
Do not run this in production, it's not designed to be a valid replacement for Apache or nginx.