/**
  * Get the headers associated to this request
  *
  * @return array Array of headers strings
  */
 public function getHeaders()
 {
     $digest = Klarna::digest(Klarna::colon($this->config['eid'], $this->params['currency'], $this->config['secret']));
     return array("Accept: {$this->accept}", "Authorization: xmlrpc-4.2 {$digest}");
 }