yii\debug\panels\LogPanel::save PHP Method

    public function save()
    {
        $target = $this->module->logTarget;
        $messages = $target->filterMessages($target->messages, Logger::LEVEL_ERROR | Logger::LEVEL_INFO | Logger::LEVEL_WARNING | Logger::LEVEL_TRACE);
        foreach ($messages as &$message) {
            // exceptions may not be serializable if in the call stack somewhere is a Closure
            if ($message[0] instanceof \Throwable || $message[0] instanceof \Exception) {
                $message[0] = (string) $message[0];
            }
        }
        return ['messages' => $messages];
    }

 /**
  * @inheritdoc
  */
 public function save()
 {
     $data = parent::save();
     return isset($data['messages']) && count($data['messages']) > 0 ? $data : null;
 }