private function headersFromFormat($format)
	{
		$type = gettype($format);
		if($type === 'array')
		{
			$headers = $format;
		}
		else if($type === 'string')
		{
			$headers = array();
			switch ($format) 
			{
				case 'json':
					$contentType = 'application/json';
					break;
				case 'jsonp':
					$contentType = 'application/javascript';
					break;
				default:
					$contentType = 'text/plain';
					break;
			}
			$headers['Content-Type'] = $contentType;
		}
		return $headers;
	}