I find that sometimes the lenght of the array in userdata[‘whence’] will less than the maxhence, so I add one more condition checking at line 15:

if(!isset($this->_ci->session->userdata[‘whence’]) || count($this->_ci->session->userdata[‘whence’]) < $this->maxwhence)
      {
        $this->clearwhence();
      }

Eh? Where is the redirect function loaded? I don’t see any instance of a call to $this->load->helper(‘url’);