v.1.5.5f PHP7.1

I would like to modify which categories actually show up on the main page when admin/configuration/layout settings/Categories - Always show on Main Page is set to on .... there are some I do not want on the main page.

In an 'associated' thread Design75 kindly suggested the file to modify was includes\modules\pages\index\main_template_vars.php .... the problem I have is that it looks far too confusing to me, too many sections that could be modified but likely shouldn't.

So can someone please give me a helping hand to isolate which section should be modified and an example please of 'how' it should be modified to exclude certain categories.

many thanks,
Mike

Code:
<?php
/**
 * index main_template_vars.php 
 *
 * @package page
 * @copyright Copyright 2003-2016 Zen Cart Development Team
 * @copyright Portions Copyright 2003 osCommerce
 * @license http://www.zen-cart.com/license/2_0.txt GNU Public License V2.0
 * @version $Id: Author: DrByte  Thu Jan 7 22:43:33 2016 -0500 Modified in v1.5.5 $
 */

// This should be first line of the script:
$zco_notifier->notify('NOTIFY_HEADER_START_INDEX_MAIN_TEMPLATE_VARS');

//die($category_depth);
//die($_GET['music_genre_id']);

// release manufacturers_id when nothing is there so a blank filter is not setup.
// this will result in the home page, if used
if (isset($_GET['manufacturers_id']) && $_GET['manufacturers_id'] <= 0) {
  unset($_GET['manufacturers_id']);
  unset($manufacturers_id);
}

// release music_genre_id when nothing is there so a blank filter is not setup.
// this will result in the home page, if used
if (isset($_GET['music_genre_id']) && $_GET['music_genre_id'] <= 0) {
  unset($_GET['music_genre_id']);
  unset($music_genre_id);
}

// release record_company_id when nothing is there so a blank filter is not setup.
// this will result in the home page, if used
if (isset($_GET['record_company_id']) && $_GET['record_company_id'] <= 0) {
  unset($_GET['record_company_id']);
  unset($record_company_id);
}

// only release typefilter if both record_company_id and music_genre_id are blank
// this will result in the home page, if used
if ((isset($_GET['record_company_id']) && $_GET['record_company_id'] <= 0) and (isset($_GET['music_genre_id']) && $_GET['music_genre_id'] <= 0) ) {
  unset($_GET['typefilter']);
  unset($typefilter);
}

// release filter for category or manufacturer when nothing is there
if (isset($_GET['filter_id']) && $_GET['filter_id'] <= 0) {
  unset($_GET['filter_id']);
  unset($filter_id);
}

// release alpha filter when nothing is there
if (isset($_GET['alpha_filter_id']) && $_GET['alpha_filter_id'] <= 0) {
  unset($_GET['alpha_filter_id']);
  unset($alpha_filter_id);
}

// hook to notifier so that additional product-type-specific vars can be released too
$zco_notifier->notify('NOTIFY_HEADER_INDEX_MAIN_TEMPLATE_VARS_RELEASE_PRODUCT_TYPE_VARS');


if ($category_depth == 'nested')
{
  $sql = "SELECT cd.categories_name, c.categories_image
          FROM   " . TABLE_CATEGORIES . " c, " . TABLE_CATEGORIES_DESCRIPTION . " cd
          WHERE      c.categories_id = :categoriesID
          AND        cd.categories_id = :categoriesID
          AND        cd.language_id = :languagesID
          AND        c.categories_status= '1'";

  $sql = $db->bindVars($sql, ':categoriesID', $current_category_id, 'integer');
  $sql = $db->bindVars($sql, ':languagesID', $_SESSION['languages_id'], 'integer');
  $category = $db->Execute($sql);

  if (isset($cPath) && strpos($cPath, '_'))
  {
    // check to see if there are deeper categories within the current category
    $category_links = array_reverse($cPath_array);
    for($i=0, $n=sizeof($category_links); $i<$n; $i++)
    {
      $sql = "SELECT count(*) AS total
              FROM   " . TABLE_CATEGORIES . " c, " . TABLE_CATEGORIES_DESCRIPTION . " cd
              WHERE      c.parent_id = :parentID
              AND        c.categories_id = cd.categories_id
              AND        cd.language_id = :languagesID
              AND        c.categories_status= '1'";

      $sql = $db->bindVars($sql, ':parentID', $category_links[$i], 'integer');
      $sql = $db->bindVars($sql, ':languagesID', $_SESSION['languages_id'], 'integer');
      $categories = $db->Execute($sql);

      if ($categories->fields['total'] < 1)
      {
        // do nothing, go through the loop
      } else {
        $categories_query = "SELECT c.categories_id, cd.categories_name, c.categories_image, c.parent_id
                             FROM   " . TABLE_CATEGORIES . " c, " . TABLE_CATEGORIES_DESCRIPTION . " cd
                             WHERE      c.parent_id = :parentID
                             AND        c.categories_id = cd.categories_id
                             AND        cd.language_id = :languagesID
                             AND        c.categories_status= '1'
                             ORDER BY   sort_order, cd.categories_name";

        $categories_query = $db->bindVars($categories_query, ':parentID', $category_links[$i], 'integer');
        $categories_query = $db->bindVars($categories_query, ':languagesID', $_SESSION['languages_id'], 'integer');
        break; // we've found the deepest category the customer is in
      }
    }
  } else {
    $categories_query = "SELECT c.categories_id, cd.categories_name, c.categories_image, c.parent_id
                         FROM   " . TABLE_CATEGORIES . " c, " . TABLE_CATEGORIES_DESCRIPTION . " cd
                         WHERE      c.parent_id = :parentID
                         AND        c.categories_id = cd.categories_id
                         AND        cd.language_id = :languagesID
                         AND        c.categories_status= '1'
                         ORDER BY   sort_order, cd.categories_name";

    $categories_query = $db->bindVars($categories_query, ':parentID', $current_category_id, 'integer');
    $categories_query = $db->bindVars($categories_query, ':languagesID', $_SESSION['languages_id'], 'integer');
  }
  $categories = $db->Execute($categories_query);
  $number_of_categories = $categories->RecordCount();
  $new_products_category_id = $current_category_id;

  /////////////////////////////////////////////////////////////////////////////////////////////////////
  $tpl_page_body = 'tpl_index_categories.php';
  /////////////////////////////////////////////////////////////////////////////////////////////////////

  //  } elseif ($category_depth == 'products' || isset($_GET['manufacturers_id']) || isset($_GET['music_genre_id'])) {
} elseif ($category_depth == 'products' || zen_check_url_get_terms()) {
  if (SHOW_PRODUCT_INFO_ALL_PRODUCTS == '1') {
    // set a category filter
    $new_products_category_id = $cPath;
  } else {
    // do not set the category
  }
  // create column list
  $define_list = array('PRODUCT_LIST_MODEL' => PRODUCT_LIST_MODEL,
  'PRODUCT_LIST_NAME' => PRODUCT_LIST_NAME,
  'PRODUCT_LIST_MANUFACTURER' => PRODUCT_LIST_MANUFACTURER,
  'PRODUCT_LIST_PRICE' => PRODUCT_LIST_PRICE,
  'PRODUCT_LIST_QUANTITY' => PRODUCT_LIST_QUANTITY,
  'PRODUCT_LIST_WEIGHT' => PRODUCT_LIST_WEIGHT,
  'PRODUCT_LIST_IMAGE' => PRODUCT_LIST_IMAGE);

  /*                         ,
  'PRODUCT_LIST_BUY_NOW' => PRODUCT_LIST_BUY_NOW);
  */
  asort($define_list);
  reset($define_list);
  $column_list = array();
  foreach ($define_list as $key => $value)
  {
    if ($value > 0) $column_list[] = $key;
  }

  $select_column_list = '';

  for ($i=0, $n=sizeof($column_list); $i<$n; $i++)
  {
    switch ($column_list[$i])
    {
      case 'PRODUCT_LIST_MODEL':
      $select_column_list .= 'p.products_model, ';
      break;
      case 'PRODUCT_LIST_NAME':
      $select_column_list .= 'pd.products_name, ';
      break;
      case 'PRODUCT_LIST_MANUFACTURER':
      $select_column_list .= 'm.manufacturers_name, ';
      break;
      case 'PRODUCT_LIST_QUANTITY':
      $select_column_list .= 'p.products_quantity, ';
      break;
      case 'PRODUCT_LIST_IMAGE':
      $select_column_list .= 'p.products_image, ';
      break;
      case 'PRODUCT_LIST_WEIGHT':
      $select_column_list .= 'p.products_weight, ';
      break;
    }
  }
  // always add quantity regardless of whether or not it is in the listing for add to cart buttons
  if (PRODUCT_LIST_QUANTITY < 1) {
    $select_column_list .= 'p.products_quantity, ';
  }

  // set the product filters according to selected product type
  $typefilter = 'default';
  if (isset($_GET['typefilter'])) $typefilter = $_GET['typefilter'];
  require(zen_get_index_filters_directory($typefilter . '_filter.php'));



  ////////////////////////////////////////////////////////////////////////////////////////////////////////////
  $tpl_page_body = 'tpl_index_product_list.php';
  ////////////////////////////////////////////////////////////////////////////////////////////////////////////
} else {
  ////////////////////////////////////////////////////////////////////////////////////////////////////////////
  $tpl_page_body = 'tpl_index_default.php';
  ////////////////////////////////////////////////////////////////////////////////////////////////////////////
}
$current_categories_description = "";
$current_categories_name = "";
// categories_description
$sql = "SELECT categories_description, categories_name
        FROM " . TABLE_CATEGORIES_DESCRIPTION . "
        WHERE categories_id= :categoriesID
        AND language_id = :languagesID";

$sql = $db->bindVars($sql, ':categoriesID', $current_category_id, 'integer');
$sql = $db->bindVars($sql, ':languagesID', $_SESSION['languages_id'], 'integer');
$categories_description_lookup = $db->Execute($sql);
if ($categories_description_lookup->RecordCount() > 0) {
  $current_categories_description = $categories_description_lookup->fields['categories_description'];
  $current_categories_name = $categories_description_lookup->fields['categories_name'];
}

if ($current_categories_name == '' && isset($_GET['manufacturers_id'])) {
  $result = $db->Execute( "SELECT * FROM " . TABLE_MANUFACTURERS . "
                           WHERE manufacturers_id = " . (int)$_GET['manufacturers_id'] . " LIMIT 1");
  if (!$result->EOF) $current_categories_name = $result->fields['manufacturers_name'];
}
if ($current_categories_name == '' && isset($_GET['record_company_id'])) {
  $result = $db->Execute( "SELECT * FROM " . TABLE_RECORD_COMPANY . "
                           WHERE record_company_id = " . (int)$_GET['record_company_id'] . " LIMIT 1");
  if (!$result->EOF) $current_categories_name = $result->fields['record_company_name'];
}
if ($current_categories_name == '' && isset($_GET['music_genre_id'])) {
  $result = $db->Execute( "SELECT * FROM " . TABLE_MUSIC_GENRE . "
                           WHERE music_genre_id = " . (int)$_GET['music_genre_id'] . " LIMIT 1");
  if (!$result->EOF) $current_categories_name = $result->fields['music_genre_name'];
}
$zco_notifier->notify('NOTIFY_HEADER_INDEX_MAIN_TEMPLATE_VARS_PAGE_BODY', NULL, $tpl_page_body, $current_categories_name);

require($template->get_template_dir($tpl_page_body, DIR_WS_TEMPLATE, $current_page_base,'templates'). '/' . $tpl_page_body);

// This should be last line of the script:
$zco_notifier->notify('NOTIFY_HEADER_END_INDEX_MAIN_TEMPLATE_VARS', NULL, $current_categories_description);