如何设置$config[' sess_expire '] codeigniter from model


How to set $config['sess_expiration'] codeigniter from model?

如何从user的设置设置会话销毁?

设置
$ses_destroy = $this->loginmodel->set_session_destroy();
$config['sess_expiration'] = $ses_destroy; 

模型
function sessions_destroy_user(){
  return echo '30';
}
$this->session->sess_expiration = '14400';// expires in 4 hours
$this->session->set_userdata($data);// set session