I'm not familiar with the PHP standard environment nor if laravel will run on standard env, but you should, for the most part, be able to swap out the app.yaml for the settings for the standard environment.
Key bits are located under the "Selecting PHP runtime" at:
https://cloud.google.com/appengine/docs/standard/php/runtimeYou'll need to remove the `env: flex` bit from app.yaml and should be able to deploy as normal.
~ Blaine