Linea21

http://phpsnips.com/571/Check-if-we-are-using-HTTPS-or-not#.WD8GQWcdN5E

http://stackoverflow.com/questions/5100189/use-php-to-check-if-page-was-accessed-with-ssl

function is_https(){
    if ( (!empty($_SERVER['HTTPS']) && $_SERVER['HTTPS'] !== 'off') || $_SERVER['SERVER_PORT'] == 443)
        return true;
    else
        return false;
}