vusys/laravel-nestedset is a modern nested-set implementation for Laravel. I tried to include everything and the kitchen sink with this package. It does not merely calculate left and right values for you, it can also calculate and keep in lock-step aggregates.
Unlike my other packages which use mkdocs for their documentation, this has a custom markdown to html build script in the repo. This is part not-invented-here, but also the documentation includes a number of interactive demos.