code: public function output($options = array())
      {
          $cfgRestore = $this->config->setCfg($options);
          if (!$this->cfg['output']) {
              $this->config->setCfg($cfgRestore);
              return null;
          }
          /*
              I'd like to put this outputAs setting bit inside Output::onOutput
              but, adding a debug.output subscriber from within a debug.output subscriber = fail
          */
          $outputAs = $this->output->getCfg('outputAs');
          if (\is_string($outputAs)) {
              $this->output->setCfg('outputAs', $outputAs);
          }
          /*
              Publish debug.output on all descendant channels and then ourself
          */
          $channels = $this->getChannels(true);
          $channels[] = $this;
          $headers = array();
          foreach ($channels as $channel) {
              $event = $channel->eventManager->publish(
                  'debug.output',
                  $channel,
                  array(
                      'headers' => array(),
                      'return' => '',
                      'isTarget' => $channel === $this,
                  )
              );
              $headers = \array_merge($headers, $event['headers']);
          }
          if (!$this->getCfg('outputHeaders') || !$headers) {
              $this->data['headers'] = \array_merge($this->data['headers'], $event['headers']);
          } elseif (\headers_sent($file, $line)) {
              \trigger_error('PHPDebugConsole: headers already sent: '.$file.', line '.$line, E_USER_NOTICE);
          } else {
              foreach ($headers as $nameVal) {
                  \header($nameVal[0].': '.$nameVal[1]);
              }
          }
          if (!$this->parentInstance) {
              $this->data['outputSent'] = true;
          }
          $this->config->setCfg($cfgRestore);
          return $event['return'];
      }
docs: Publishes debug.output event and returns result
  
  @param array $options Override any output options
  
  @return string|null