As per the MediaWiki version lifecycle, I would like to announce the formal end of life (EOL) of MediaWiki 1.31 as of tomorrow, Thursday September 30, 2021, coinciding with the final security and maintenance release for the branch, 1.31.16.
This means that MediaWiki 1.31 will no longer receive maintenance or security backports. It is therefore strongly discouraged that you continue to use it.
It is recommended to upgrade to MediaWiki 1.35, the current Long Term Support (LTS) version which is not due to become EOL until September 2023.
MediaWiki 1.35 bumps the required PHP version from 7.0 in 1.31 (which is unsupported upstream), to PHP 7.3.19 or later.