Try something like this:
$limesurvey = new jsonRPCClient('http://localhost/limesurvey/index.php/admin/remotecontrol/');
$sessionKey = $limesurvey->get_session_key('adminusername', 'adminpassword');
$survey = $limesurvey->add_survey($sessionKey, null, 'Survey Title', 'en', 'S');
$limesurvey->release_session_key($sessionKey);
passing null as the survey ID will have limesurvey generate one for you.
You will probably need to change the URL to the limesurvey installation (in this case http://localhost/limesurvey) as well as the username and password parameters of the get_session_key function