There has been a critical error on this website – wordpress issue after upgrading PHP

(Documenting the actual solution for when PHP 8.3 goes EOL.) Open up your php.ini and search for mysqli. You’ll find a line where the mysqli extension is commented out with a semicolon. Remove the semicolon, save the file and restart the webserver (Apache/nginx/whatever).

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)