I have a media wiki version 1.23 and php version : 5.5.6. Now I want to upgrade it to media wiki 1.42 and php 8.3. How can I do this? I am using XAMMP server in Windows.
Topic on Manual talk:Upgrading
I already replied below, but...
The starting point would be to read Manual:Upgrading carefully, because that's a big jump. As it says there, if you want to upgrade without losing data you're going to have to do it in (at least) two stages: First you'll need to upgrade to 1.35, as it's not safe to upgrade from older versions to 1.39 or later. Then when you've got it upgraded to 1.35, you can upgrade to 1.42.
When actually doing the upgrades, you should follow the instructions found in the UPGRADE text file in each distribution (first 1.35, then 1.42).