how to create a recursive function in vbb

[Dev.Sun]

I got a Fatal error

Fatal error: Call to a member function query_read() on a non-object in public_html/vbbtest/includes/adminfunctions_navbarmanager.php on line 36

Bellow is my code and recursive function

PHP Code:

    $navbars = $db->query_read ("SELECT * FROM " . TABLE_PREFIX . "navbar_manager ORDER BY navbarid ASC,sortorder ASC");
    while ($navbar = $db->fetch_array ($navbars))
    {
        $mc++;
        print_cells_row (array ($navbar['navbarname'], 
                                $navbar['navbarname'], 
                                $navbar['sortorder'],
            construct_link_code ($vbphrase['edit'], "navbar_manager.php?" . $vbulletin->session->vars['sessionurl'] . "do=manager&so=edit&navbarid=$navbar[navbarid]") .
            construct_link_code ($vbphrase['delete'], "navbar_manager.php?" . $vbulletin->session->vars['sessionurl'] . "do=manager&so=delete&navbarid=$navbar[navbarid]")
        ));
    
        getMenucon($navbar['navbarid']);    
    } 


recursive function

PHP Code:


function getMenucon($id_cha){
    $sqlMenuCon = $db->query_read("SELECT * FROM " . TABLE_PREFIX . "navbar_manager WHERE navbarparentid = ". intval ($id_cha) ." order by sortorder");
    while($navbar2 = $db->fetch_array($sqlMenuCon))
    {
        print_cells_row (array ($navbar['navbarname'], 
                                        $navbar['navbarname'], 
                                        $navbar['sortorder'],
                    construct_link_code ($vbphrase['edit'], "navbar_manager.php?" . $vbulletin->session->vars['sessionurl'] . "do=manager&so=edit&navbarid=$navbar[navbarid]") .
                    construct_link_code ($vbphrase['delete'], "navbar_manager.php?" . $vbulletin->session->vars['sessionurl'] . "do=manager&so=delete&navbarid=$navbar[navbarid]")
                ));
    }  
} 


this code work when i test out site vbulletin.

Anybody can help me?