Piwik\SettingsPiwik::isSameFingerprintAcrossWebsites PHP Method

    public static function isSameFingerprintAcrossWebsites()
    {
        return (bool) Config::getInstance()->Tracker['enable_fingerprinting_across_websites'];
    }

 protected function enrichWithUniqueVisitorsMetric(Row $row)
 {
     // skip unique visitors metrics calculation if calculating for multiple sites is disabled
     if (!$this->getParams()->isSingleSite() && $this->skipUniqueVisitorsCalculationForMultipleSites) {
         return;
     }
     if ($row->getColumn('nb_uniq_visitors') === false && $row->getColumn('nb_users') === false) {
         return;
     }
     if (!SettingsPiwik::isUniqueVisitorsEnabled($this->getParams()->getPeriod()->getLabel())) {
         $row->deleteColumn('nb_uniq_visitors');
         $row->deleteColumn('nb_users');
         return;
     }
     $metrics = array(Metrics::INDEX_NB_USERS);
     if ($this->getParams()->isSingleSite()) {
         $uniqueVisitorsMetric = Metrics::INDEX_NB_UNIQ_VISITORS;
     } else {
         if (!SettingsPiwik::isSameFingerprintAcrossWebsites()) {
             throw new Exception("Processing unique visitors across websites is enabled for this instance,\n                            but to process this metric you must first set enable_fingerprinting_across_websites=1\n                            in the config file, under the [Tracker] section.");
         }
         $uniqueVisitorsMetric = Metrics::INDEX_NB_UNIQ_FINGERPRINTS;
     }
     $metrics[] = $uniqueVisitorsMetric;
     $uniques = $this->computeNbUniques($metrics);
     $row->setColumn('nb_uniq_visitors', $uniques[$uniqueVisitorsMetric]);
     $row->setColumn('nb_users', $uniques[Metrics::INDEX_NB_USERS]);
 }