Yo can simply specify MSSQL connection settins in same way what you did with MySql. Before proceeding you check xampp/wampp if php_mssql extension is enabled or not in your php configuration.
example-
$server = 'server_address';
$user = 'username';
$passwd = 'passwod';
$dbname = 'db_name';
$conn = mssql_connect($server, $user, $passwd);
mssql_select_db($dbname, $conn);