How can I create a private var to use in some functions at the same class?

class Pizzaria extends CI_Controller {
               
    private $pizzaria;
 
 function __construct()
 {
   parent::__construct();

  $this->pizzaria=array();

  init_pizzaria();
  $this->load->model('Pizzaria_model');
  $this->load->library('session');  
  $this->load->library('cart'); 
 }

 public function mostra_pizzaria(){

  $idpizzaria =$this->uri->segment(3);

  $this->pizzaria  =$this->Pizzaria_model->get_byid('id_pizzaria', $idpizzaria, 'pizzaria')->row();
  
  print_r($this->pizzaria); // this is OK!!!!!
  
  $dados = array( 'tela'   => 'mostra_pizzaria2',
      'pizzaria'   => $this->pizzaria);

  set_tema('footerinc', load_js(array('jquery-1.10.2.min','jquery.dataTables','dataTables.foundation','table')),FALSE);
  set_tema('titulo','Mostrar Pizzaria');
  set_tema('template','pizza_view');
  set_tema('conteudo', load_modulo('pizzaria_view',$dados,'pizzaria'));
  load_template();

 }


/* this function is called after a submit from view mostra_pizzaria2 */

 public function cardapio(){

  $idx_cardapio=$this->input->post('item_cardapio');

  print_r($this->pizzaria);  // this is empty!!!!!!

  print_r($idx_cardapio);
}

}

case 'mostra_pizzaria2':

       echo '<div class="large-6 columns">';
       echo '<div class="row"';

       echo form_label('Filtrar Cardapio');

       echo form_open("pizzaria/cardapio", array('class'=>'custom'));  
       echo form_dropdown('item_cardapio', $cardapio, $idx_cardapio);
       echo form_submit(array('name'=>'filtrar_cardapio','class'=>'button radius tiny'),'Filtrar Cardapio');  

       echo form_close();

       echo '</div>';
       echo '</div>';

             break;