In my desktop XAMPP test environment, phpinfo.php is reporting a successful PHP 7.1.18 install. I changed
$dbms = 'mysql';to
$dbms = 'mysqli';in config.php, and purged the cache - but I'm getting the dreaded:
phpinfo.php reports that mysqlnd is installed, but not mysqli. Does mysqlnd provide support for mysqli calls?General Error
SQL ERROR [ mysqli ]
mysqli_connect function does not exist, is mysqli extension installed? 
In any event, I'm at a loss as to next steps. Can anyone advise?