Yes. You are right.
This is awesome THE PluginLibrary created by frostschutz, a bunch of helper functions to ease the base coding of MyBB Plugins. Here we intend to maintain this epic creation to work with latest PHP and MyBB Versions.

 

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PluginLibrary for MyBB (Updated for PHP 8)
A collection of useful functions used by other plugins.

https://github.com/mybbgroup/MyBB-PluginLibrary

PHP 8 update forked from the original at:
https://github.com/frostschutz/MyBB-PluginLibrary

Users:

Upload inc/plugins/pluginlibrary.php to your inc/plugins/ folder.
No other files are required and no further steps are necessary.

Developers:

Please refer to PluginLibrary-Documentation.html and / or
to the sample plugin inc/plugins/hello_pl.php for detailed information
on how to use PluginLibrary with your own plugins.