/**
  * The deleteCampaign method checks if a campaign ID exists and
  * modifies the details for the campaign if it exists or returns an error
  * message, as appropriate.
  *
  * @access public
  *
  * @param string $sessionId
  * @param integer $campaignId
  *
  * @return boolean
  */
 function deleteCampaign($sessionId, $campaignId)
 {
     if ($this->verifySession($sessionId)) {
         return $this->_validateResult($this->_dllCampaign->delete($campaignId));
     } else {
         return false;
     }
 }