Where would one get started with PHP without picking up Laravel or Drupal?

* https://symfony.com

* https://getcomposer.org

* https://www.php-fig.org/psr/

Every PHP file can work without frameworks. The route is your filename, PHP by itself can do templating and input data is handled by the super globals.

But if you want some small and simple framework as guidance you can also try out Slim Framework.

https://www.processwire.com