update closed column in database using button click

so i've been trying to do this multiple times but stil didnt get the answer. i have a column named closed in my database and close button in my view, whenever i click the button close, i want it to update my closed column to '0' if it is closed and '1' if it still open. below is my code in controller, sorry im still new to this.

Public function close(){

      $pvar = array();
      $pid = $this->uri->segment(1, 0);
      $iid = $this->uri->segment(2, 0);
      $pageisx = $this->uri->segment(3, 0);
      $pagei = 'Purchase Order';
      $iuser = $this->users->chkadmin();
      $gpost = $this->input->post(NULL, TRUE);
      $pvar['pageimenu'] = 'purchasing';
      $pvar['htitle'] = 'Purchase: '.$iid;

      $this->db->select('*');
      $this->db->from('po');
      $this->db->where('po.pono', $iid);
      $this->db->order_by('po.pono', 'DESC');

      $pvar['purchaseorder'] = $this->db->get()->row_array();

      if (isset($gpost['close']))
      {
        if (isset($gpost['locode'])) {
          $getlo = $gpost['locode'];
          if ($getlo == $this->session->skey) {
            foreach ($gpost['close'] as $k => $x) {

              $close = 1;
              $c['closed'] = $close;

              //$close = $this->input->post('1');

                $this->db->set('closed', 1 );
                $this->db->where('po.id', $k);
                $this->db->update('po');
              }

        redirect(base_url().'purchaseorderlist.php');
      }}}

        $pvar['css'] = '
        <link href="'.base_url().'css/manage.css" rel="stylesheet" type="text/css" />
      ';
      $pvar['pc'] = $this->load->view('purchasing/purchaseorderview', $pvar, TRUE);
      $this->load->view('home', $pvar);
      }

i use codeigniter btw....thanks