You should enable php_mysqli extension in PHP.ini. It’s disabled by default.
look for the following line: extension=php_mysqli
also, check that you’re supplying the port in the connection if you’re using a non-standard port
i.e.
$gaSql[‘link’] = mysqli_connect($gaSql[‘server’], $gaSql[‘user’], $gaSql[‘password’],$gaSql[‘db’],$gaSql[‘port’]) or die(“Error ” . mysqli_error($gaSql[‘link’]));