If you want to take right results for traffic summary you need to use following parameters:
$siteId - unique site identificator, it sets at config file 'includes/config.php'
$apiKey - api key for your website
$outputType - it's a type of your output, you need set it as 'XML', 'PHP' or 'JSON'
XML - return results at XML format, PHP - serialize array, JSON - JSON format
$date - date range for your requests, format is "YYYY-MM-DD, YYYY-MM-DD"