session problem in pagination

[eluser]rajyakshmik[/eluser]
same problem.I m using like this

Code:

else if($key == 'S1')
        {
            $session = array(
                           'zip' => $this->input->post('zip')                
                           );
             $this->session->set_userdata($session);
        }

Code:

if($this->session->userdata('zip')!='')
        {
            $szip = $this->session->userdata('zip');
            $condi.= " and merchants.zip ='$szip'";
        }