code: function timerCallback() {
          if (!$this->_enabled)
              return;
          $now = time();
          foreach ($this->_tasks as $name => &$task) {
              if ($task[0] > $now)
                  continue;
              call_user_func_array($task[1], [&$task[0], &$task[3], &$task[2]]);
              if (!$task[3])
                  unset($this->_tasks[$name]);
          }
      }
docs: 定时器回调