How to include IntelliSense substitution libraries in VSCode?

Question

PHP

Dear Gurus, please advise.
How to include library for Intellisense.
For example, I am writing a module for a CMS. In the project folder, I only have this module. but for command substitution, you need to have the commands of the entire CMS in the Instellisense substitution list.
The module is located in a subfolder of a subfolder of the CMS subfolder. It is not possible as a project to use the entire CMS, especially since it is difficult to deploy only the module and not the entire CMS.
How to connect separate libraries for Intellisense?