I would like to replace the ancient Mediawiki (version 1.21.2,l PHP version 5.3.3, MySQL 5.1.73) used by my company with a brand new Mediawiki site running the latest version (requires php 7.0.13 or newer) and with brand new content.
Naturally, I'd like to leave the old wiki intact until the new wiki surpasses it. The old wiki is on http://XX.XX.XX.XX:800. I'd like the new wiki to be simultaneously available on http://XX.XX.XX.XX:801.
I've tried to upgrading removing php 5.3 and installing php 7.1 (from this site) but the old wiki was no longer accessible after the install. It appears that the old mediawiki was incompatible with php 7.1, so I had to roll back to php 5.3.