public function getLinkingMethod(Pap_Common_Banner $banner = null) {
     if ($banner != null && $banner->getCampaignId() != '') {
         $campaign = new Pap_Common_Campaign();
         $campaign->setId($banner->getCampaignId());
         $campaign->load();
         if ($campaign->getLinkingMethod() != self::LINKMETHOD_DEFAULT_VALUE && 
             $campaign->getLinkingMethod() != null &&
             $campaign->getLinkingMethod() != '') {
             return $campaign->getLinkingMethod();
         }
     }
     return Gpf_Settings::get(Pap_Settings::SETTING_LINKING_METHOD);
 }