/**
  * Call this only if you are actually showing the page.
  */
 public function initialize()
 {
     $page_hook = wpcf_admin_add_submenu_page(array('menu_title' => $this->get_title(), 'function' => array($this, 'page_handler'), 'capability_filter' => 'wpcf_tfc_view'), wpcf_getget('page'));
     // I hate having to do this. Refactor!
     require_once WPCF_INC_ABSPATH . '/fields.php';
     wpcf_fields_contol_common_resources();
     add_action("load-{$page_hook}", array($this, 'add_screen_options'));
 }

 function setup_installer()
 {
     if (isset($_GET['page']) && 'installer' == $_GET['page']) {
         wpcf_admin_add_submenu_page(array('menu_title' => __('Installer', 'wpcf'), 'menu_slug' => 'installer', 'function' => 'installer_content'));
     }
 }

 /**
  * add Getting Started to menu
  */
 public function add_getting_started_to_admin_menu()
 {
     $menu = array('page_title' => __('What kind of site are you building?', 'wpcf'), 'menu_title' => __('Getting Started', 'wpcf'), 'menu_slug' => basename(dirname(dirname(__FILE__))) . '/marketing/getting-started/index.php', 'hook' => 'wpcf_marketing', 'load_hook' => 'wpcf_marketing_hook');
     wpcf_admin_add_submenu_page($menu);
 }

function wpcf_admin_add_submenu_page($menu, $menu_slug = null, $menu_parent = 'wpcf')
{
    if (!is_admin()) {
        return;
    }
    $menu_slug = array_key_exists('menu_slug', $menu) ? $menu['menu_slug'] : $menu_slug;
    $capability = array_key_exists('capability', $menu) ? $menu['capability'] : 'manage_options';
    $wpcf_capability = apply_filters('wpcf_capability', $capability, $menu, $menu_slug);
    $wpcf_capability = apply_filters('wpcf_capability' . $menu_slug, $capability, $menu, $menu_slug);
    /**
     * allow change capability  by filter
     * full list https://goo.gl/OJYTvl
     */
    if (isset($menu['capability_filter'])) {
        $wpcf_capability = apply_filters($menu['capability_filter'], $wpcf_capability, $menu, $menu_slug);
    }
    /**
     * add submenu
     */
    $hook = add_submenu_page($menu_parent, isset($menu['page_title']) ? $menu['page_title'] : $menu['menu_title'], $menu['menu_title'], $wpcf_capability, $menu_slug, array_key_exists('function', $menu) ? $menu['function'] : null);
    // For given menu slug, publish the final hook name in case we need it somewhere.
    do_action("wpcf_admin_add_submenu_page_{$menu_slug}", $hook);
    if (!empty($menu_slug)) {
        wpcf_admin_plugin_help($hook, $menu_slug);
    }
    /**
     * add action
     */
    if (!array_key_exists('load_hook', $menu) && array_key_exists('function', $menu) && is_string($menu['function'])) {
        $menu['load_hook'] = sprintf('%s_hook', $menu['function']);
    }
    if (!empty($menu['load_hook']) && function_exists($menu['load_hook'])) {
        $action = sprintf('load-%s', array_key_exists('hook', $menu) ? $menu['hook'] : $hook);
        add_action($action, $menu['load_hook']);
    }
    /**
     * add submenu to submenu
     */
    if (array_key_exists('submenu', $menu)) {
        foreach ($menu['submenu'] as $submenu_slug => $submenu) {
            wpcf_admin_add_submenu_page($submenu, $submenu_slug, $hook);
        }
    }
    return $hook;
}

/**
 * Teaser menu hook.
 */
function wpcf_access_teaser_admin_menu()
{
    $hook = wpcf_admin_add_submenu_page(array('page_title' => __('Access Control and User Roles', 'wpcf'), 'menu_title' => __('Access Control and User Roles', 'wpcf'), 'menu_slug' => 'wpcf-access', 'function' => 'wpcf_access_teaser_admin_menu_page', 'load_hook' => 'wpcf_access_teaser_admin_menu_load'));
}

 function setup_installer()
 {
     wpcf_admin_add_submenu_page(array('page_title' => __('Installer', 'wpcf'), 'menu_title' => __('Installer', 'wpcf'), 'menu_slug' => 'installer', 'function' => 'installer_content'));
 }

function wpcf_admin_add_submenu_page($menu, $menu_slug = null, $menu_parent = 'wpcf')
{
    if (!is_admin()) {
        return;
    }
    $wpcf_capability = apply_filters('wpcf_capability', 'manage_options');
    $menu_slug = array_key_exists('menu_slug', $menu) ? $menu['menu_slug'] : $menu_slug;
    /**
     * add submenu
     */
    $hook = add_submenu_page($menu_parent, isset($menu['page_title']) ? $menu['page_title'] : $menu['menu_title'], $menu['menu_title'], $wpcf_capability, $menu_slug, array_key_exists('function', $menu) ? $menu['function'] : null);
    if (!empty($menu_slug)) {
        wpcf_admin_plugin_help($hook, $menu_slug);
    }
    /**
     * add action
     */
    if (!array_key_exists('load_hook', $menu) && array_key_exists('function', $menu)) {
        $menu['load_hook'] = sprintf('%s_hook', $menu['function']);
    }
    if (!empty($menu['load_hook']) && function_exists($menu['load_hook'])) {
        $action = sprintf('load-%s', array_key_exists('hook', $menu) ? $menu['hook'] : $hook);
        add_action($action, $menu['load_hook']);
    }
    /**
     * add submenu to submenu
     */
    if (array_key_exists('submenu', $menu)) {
        foreach ($menu['submenu'] as $submenu_slug => $submenu) {
            wpcf_admin_add_submenu_page($submenu, $submenu_slug, $hook);
        }
    }
    return $hook;
}

 /**
  * add Getting Started to menu
  */
 public function add_getting_started_to_admin_menu()
 {
     if (!isset($_REQUEST['page'])) {
         return;
     }
     $slug = basename(dirname(dirname(dirname(__FILE__)))) . '/marketing/getting-started/index.php';
     if ($_REQUEST['page'] != $slug) {
         return;
     }
     $menu = array('page_title' => __('What kind of site are you building?', 'wpcf'), 'menu_title' => __('Getting Started', 'wpcf'), 'menu_slug' => $slug, 'hook' => 'wpcf_marketing', 'load_hook' => 'wpcf_marketing_hook');
     wpcf_admin_add_submenu_page($menu);
 }

/**
 * Teaser menu hook.
 */
function wpcf_access_teaser_admin_menu()
{
    if (isset($_GET['page']) && 'wpcf-access' == $_GET['page']) {
        $hook = wpcf_admin_add_submenu_page(array('menu_title' => __('Access', 'wpcf'), 'menu_slug' => 'wpcf-access', 'function' => 'wpcf_access_teaser_admin_menu_page', 'load_hook' => 'wpcf_access_teaser_admin_menu_load'));
    }
}