Whats the point of Server::getInstance() if your not suppose to use it? And yes before yall start spamming with learn php blah blah blah yes i know your supposed to use getServer()
Having such function present doesn't mean you should use it. It was supposed to be used, but since some pthreads issues emerged, it is discouraged to be used.
It is called a singleton and it is completely valid design pattern. You can read more about it at http://www.phptherightway.com/pages/Design-Patterns.html
Not for me, you can look at the page source on GitHub at https://github.com/codeguy/php-the-right-way/blob/gh-pages/pages/Design-Patterns.md