Can you tell me a simple and reliable wiki engine?

Question

Knowledge base

Actually, I read several similar questions, but still - they are not quite about that.
What you want:
01. a free wiki engine
02. very desirable in php
03. if possible - integration with slack and worksection "out of the box"
04. use of Markdown (although this is by itself?)
05. not a SaaS solution, but to you could completely put it on your server
Or maybe not a wiki at all, but some other format for the knowledge base (not for clients, but for internal use in the first place)

Answer 1

xwiki.org
XWiki is a second generation wiki written in Java, distributed under the LGPL, features include a blog, API tools, comments, LDAP authentication, page export to PDF. Used by many companies around the world. 25 interface languages, including Russian.
There are:
— Ability to edit and create new macros;
- Script programming capabilities (Velocity, Groovy, Python, Ruby and PHP) and syntax support for popular Wiki engines (Confluence, JSPWiki, Creole, MediaWiki, and TWik);

Answer 2

Choose ...

Answer 3

https://www.mediawiki.org/wiki/MediaWiki/ru