code: public function writeDebugLog(...$args)
      {
          //    Only write the debug log if logging is enabled
          if ($this->writeDebugLog) {
              $message = implode($args);
              $cellReference = implode(' -> ', $this->cellStack->showStack());
              if ($this->echoDebugLog) {
                  echo $cellReference,
                      ($this->cellStack->count() > 0 ? ' => ' : ''),
                      $message,
                      PHP_EOL;
              }
              $this->debugLog[] = $cellReference .
                  ($this->cellStack->count() > 0 ? ' => ' : '') .
                  $message;
          }
      }
docs: Write an entry to the calculation engine debug log.