While this image is supposed to be a service image, you can give a try to d8 shell by running
docker run -it phpv8/php-v8 bash -c "php test.php"
This image supposed to be used to provide a complete environment to get starting with php-v8. We don't build image for every v8 tag, so if you are urgently need some specific version and you are not up to fork and setup your own docker hub repo, feels free to open an issue for that.
This repo content is licensed under the MIT license.