menu_example.module in Examples for Developers 6

Demonstrates uses of the Menu APIs in Drupal, including hook_menu(), hook_menu_alter(), and hook_menu_link_alter().

File

menu_example/menu_example.module

<?php

/**
 * @file
 * Demonstrates uses of the Menu APIs in Drupal, including hook_menu(),
 * hook_menu_alter(), and hook_menu_link_alter().
 */

/**
 * @defgroup menu_example Example: Menu API
 * @ingroup examples
 * @{
 * Examples using Menu API. (drupal 6)
 *
 * Demonstrates uses of the Menu APIs in Drupal, including hook_menu(),
 * hook_menu_alter(), and hook_menu_link_alter().
 *
 * This example is part of the Examples for Developers Project which you can download
 * and experiment with here: http://drupal.org/project/examples
 */

/**
 * Implementatation of hook_menu().
 */
function menu_example_menu() {

  // The simplest kind of menu: A simple call to a function with a menu entry.
  // The key of the menu item (menu_example/simplest) is the path that defines
  // the menu router entry.
  $items['menu_example'] = array(
    // The menu type is not required, as we're using the default.
    // 'type' => MENU_NORMAL_ITEM,
    // The title - do NOT use t() as t() is called automatically.
    'title' => 'Menu Example',
    // Description (hover flyover for menu link). Does NOT use t(), which is
    // called automatically.
    'description' => 'Simplest possible menu type, and the parent menu entry for others',
    // Function to be called when this path is accessed.
    'page callback' => '_menu_example_basic_instructions',
    // Arguments to the page callback. Here's we'll use them just to provide
    // content for our page.
    'page arguments' => array(
      t('This page is displayed by the simplest (and base) menu example. Note that the title of the page is the same as the link title. You can also <a href="!link">visit a similar page with no menu link</a>. Also, note that there is a hook_menu_alter() example that has changed the path of one of the menu items.', array(
        '!link' => url('menu_example/path_only'),
      )),
    ),
    // This is to be accessible to all users, so 'access callback' can be set
    // to TRUE, meaning that we should bypass all access checks.
    'access callback' => TRUE,
    // If the page callback is located in another file, specify it here and
    // that file will be automatically loaded when needed.
    // 'file' => 'menu_example.module',
    // We can choose which menu gets the link. The default is 'navigation'.
    // 'menu_name' => 'navigation',
    // Show the menu link as expanded.
    'expanded' => TRUE,
  );

  // Show a menu link in a menu other than the default "Navigation" menu.
  // The menu must already exist.
  $items['menu_example_alternate_menu'] = array(
    'title' => 'Menu Example: Menu in alternate menu',
    // Machine name of the menu in which the link should appear.
    'menu_name' => 'primary-links',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('This will be in the Primary Links menu instead of the default Navigation menu'),
    ),
    'access callback' => TRUE,
  );

  // A menu entry with simple permissions using user_access().
  // First, provide a courtesy menu item that mentions the existence of the
  // permissioned item.
  $items['menu_example/permissioned'] = array(
    'title' => 'Permissioned Example',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('A menu item that requires the "access protected menu example" permission is at <a href="!link">menu_example/permissioned/controlled</a>', array(
        '!link' => url('menu_example/permissioned/controlled'),
      )),
    ),
    'access callback' => TRUE,
    'expanded' => TRUE,
  );

  // Now provide the actual permissioned menu item.
  $items['menu_example/permissioned/controlled'] = array(
    // The title - do NOT use t() as t() is called automatically.
    'title' => 'Permissioned Menu Item',
    'description' => 'This menu entry will not show and the page will not be accessible without the "access protected menu example" permission.',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('This menu entry will not show and the page will not be accessible without the "access protected menu example" permission.'),
    ),
    // For a permissioned menu entry, we provide an access callback which
    // determines whether the current user should have access. The default is
    // user_access(), which we'll use in this case. Since it's the default,
    // we don't even have to enter it.
    // 'access callback' => 'user_access',
    // The 'access arguments' are passed to the 'access callback' to help it
    // do its job. In the case of user_access(), we need to pass a permission
    // as the first argument.
    'access arguments' => array(
      'access protected menu example',
    ),
    // The optional weight element tells how to order the submenu items.
    // Higher weights are "heavier", dropping to the bottom of the menu.
    'weight' => 10,
  );

  // A menu router entry with no menu link. This could be used any time we
  // don't want the user to see a link in the menu. Otherwise, it's the same
  // as the "simplest" entry above. MENU_CALLBACK is used for all menu items
  // which don't need a visible menu link, including services and other pages
  // that may be linked to but are not intended to be accessed directly.
  // First, provide a courtesy link in the menu so people can find this.
  $items['menu_example/path_only'] = array(
    'title' => 'MENU_CALLBACK example',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('A menu entry with no menu link (MENU_CALLBACK) is at <a href="!link">!link</a>', array(
        '!link' => url('menu_example/path_only/callback'),
      )),
    ),
    'access callback' => TRUE,
    'weight' => 20,
  );
  $items['menu_example/path_only/callback'] = array(
    // A type of MENU_CALLBACK means leave the path completely out of the menu
    // links.
    'type' => MENU_CALLBACK,
    // The title is still used for the page title, even though it's not used
    // for the menu link text, since there's no menu link.
    'title' => 'Callback Only',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('The menu entry for this page is of type MENU_CALLBACK, so it provides only a path but not a link in the menu links, but it is the same in every other way to the simplest example.'),
    ),
    'access callback' => TRUE,
  );

  // A menu entry with tabs.
  // For tabs we need at least 3 things:
  // 1. A parent MENU_NORMAL_ITEM menu item (menu_example/tabs in this
  //    example.)
  // 2. A primary tab (the one that is active when we land on the base menu).
  //    This tab is of type MENU_DEFAULT_LOCAL_TASK.
  // 3. Some other menu entries for the other tabs, of type MENU_LOCAL_TASK.
  $items['menu_example/tabs'] = array(
    // 'type' => MENU_NORMAL_ITEM,  // Not necessary since this is the default.
    'title' => 'Tabs',
    'description' => 'Shows how to create primary and secondary tabs',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('This is the "tabs" menu entry.'),
    ),
    'access callback' => TRUE,
    'weight' => 30,
  );

  // For the default local task, we need very little configuration, as the
  // callback and other conditions are handled by the parent callback.
  $items['menu_example/tabs/default'] = array(
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'title' => t('Default primary tab'),
    'weight' => 1,
  );

  // Now add the rest of the tab entries.
  foreach (array(
    t('second') => 2,
    t('third') => 3,
    t('fourth') => 4,
  ) as $tabname => $weight) {
    $items["menu_example/tabs/{$tabname}"] = array(
      'type' => MENU_LOCAL_TASK,
      'title' => $tabname,
      'page callback' => '_menu_example_menu_page',
      'page arguments' => array(
        t('This is the tab "@tabname" in the "basic tabs" example', array(
          '@tabname' => $tabname,
        )),
      ),
      'access callback' => TRUE,
      // The weight property overrides the default alphabetic ordering of menu
      // entries, allowing us to get our tabs in the order we want.
      'weight' => $weight,
    );
  }

  // Finally, we'll add secondary tabs to the default tab of the tabs entry.
  // The default local task needs very little information.
  $items['menu_example/tabs/default/first'] = array(
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'title' => t('Default secondary tab'),
  );
  foreach (array(
    t('second'),
    t('third'),
  ) as $tabname) {
    $items["menu_example/tabs/default/{$tabname}"] = array(
      'type' => MENU_LOCAL_TASK,
      'title' => $tabname,
      'page callback' => '_menu_example_menu_page',
      'page arguments' => array(
        t('This is the secondary tab "@tabname" in the "basic tabs" example "default" tab', array(
          '@tabname' => $tabname,
        )),
      ),
      'access callback' => TRUE,
    );
  }

  // All the portions of the URL after the base menu are passed to the page
  // callback as separate arguments, and can be captured by the page callback
  // in its argument list. Our _menu_example_menu_page() function captures
  // arguments in its function signature and can output them.
  $items['menu_example/use_url_arguments'] = array(
    'title' => 'Extra Arguments',
    'description' => 'The page callback can use the arguments provided after the path used as key',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('This page demonstrates using arguments in the path (portions of the path after "menu_example/url_arguments". For example, access it with <a href="!link1">!link1</a> or <a href="!link2">!link2</a>).', array(
        '!link1' => url('menu_example/use_url_arguments/one/two'),
        '!link2' => url('menu_example/use_url_arguments/firstarg/secondarg'),
      )),
    ),
    'access callback' => TRUE,
    'weight' => 40,
  );

  // The menu title can be dynamically created by using the 'title callback'
  // which by default is t(). Here we provide a title callback which adjusts
  // the menu title based on the current user's username.
  $items['menu_example/title_callbacks'] = array(
    'title callback' => '_menu_example_simple_title_callback',
    'title arguments' => array(
      t('Dynamic title: username='),
    ),
    'description' => 'The title of this menu item is dynamically generated',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('The menu title is dynamically changed by the title callback'),
    ),
    'access callback' => TRUE,
    'weight' => 50,
  );

  // Sometimes we need to capture a specific argument within the menu path,
  // as with the menu entry 'menu_example/placeholder_argument/3333/display',
  // where we need to capture the "3333". In that case, we use a placeholder in
  // the path provided in the menu entry. The (odd) way this is done is by using
  // array(numeric_position_value) as the value for 'page arguments'. The
  // numeric_position_value is the zero-based index of the portion of the URL
  // which should be passed to the 'page callback'.
  // First we provide a courtesy link with information on how to access
  // an item with a placeholder.
  $items['menu_example/placeholder_argument'] = array(
    'title' => 'Placeholder Arguments',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('Demonstrate placeholders by visiting <a href="!link">menu_example/placeholder_argument/3343/display</a>', array(
        '!link' => url('menu_example/placeholder_argument/3343/display'),
      )),
    ),
    'access callback' => TRUE,
    'weight' => 60,
  );

  // Now the actual entry.
  $items['menu_example/placeholder_argument/%/display'] = array(
    'title' => 'Placeholder Arguments',
    'page callback' => '_menu_example_menu_page',
    // Pass the value of '%', which is zero-based argument 2, to the
    // 'page callback'. So if the URL is
    // 'menu_example/placeholder_argument/333/display' then the value 333
    // will be passed into the 'page callback'.
    'page arguments' => array(
      2,
    ),
    'access callback' => TRUE,
  );

  // Drupal provides magic placeholder processing as well, so if the placeholder
  // is '%menu_example_arg_optional', the function
  // menu_example_arg_optional_load($arg) will be called to translate the path
  // argument to a more substantial object. $arg will be the value of the
  // placeholder. Then the return value of menu_example_id_load($arg) will be
  // passed to the 'page callback'.
  // In addition, if (in this case) menu_example_arg_optional_to_arg() exists,
  // then a menu link can be created using the results of that function as a
  // default for %menu_example_arg_optional.
  $items['menu_example/default_arg/%menu_example_arg_optional'] = array(
    'title' => 'Processed Placeholder Arguments',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      2,
    ),
    // arg 2 (3rd arg) is the one we want.
    'access callback' => TRUE,
    'weight' => 70,
  );
  $items['menu_example/menu_original_path'] = array(
    'title' => 'Menu path that will be altered by hook_menu_alter()',
    'page callback' => '_menu_example_menu_page',
    'page arguments' => array(
      t('This menu item was created strictly to allow the hook_menu_alter() function to have something to operate on. hook_menu defined the path as menu_example/menu_original_path. The hook_menu_alter() changes it to menu_example/menu_altered_path. You can try navigating to both paths and see what happens!'),
    ),
    'access callback' => TRUE,
    'weight' => 80,
  );
  return $items;
}

/**
 * Page callback for the simplest introduction menu entry.
 *
 * @param $content
 *   Some content passed in.
 */
function _menu_example_basic_instructions($content = NULL) {
  $base_content = t('This is the base page of the Menu Example. There are a number of examples
  here, from the most basic (like this one) to extravagant mappings of loaded
  placeholder arguments. Enjoy!');
  return '<div>' . $base_content . '</div><br /><div>' . $content . '</div>';
}

/**
 * Page callback for use with most of the menu entries. The arguments it
 * receives determine what it outputs.
 *
 * @param $content
 *   The base content to output.
 * @param $arg1
 *   First additional argument from the path used to access the menu
 * @param $arg2
 *   Second additional argument.
 */
function _menu_example_menu_page($content = NULL, $arg1 = NULL, $arg2 = NULL) {
  $output = '<div>' . $content . '</div>';
  if (!empty($arg1)) {
    $output .= '<div>' . t('Argument 1=%arg', array(
      '%arg' => $arg1,
    )) . '</div>';
  }
  if (!empty($arg2)) {
    $output .= '<div>' . t('Argument 2=%arg', array(
      '%arg' => $arg2,
    )) . '</div>';
  }
  return $output;
}

/**
 * Implements hook_perm() to provide a demonstration access string.
 */
function menu_example_perm() {
  return array(
    'access protected menu example',
  );
}

/**
 * Utility function to provide mappings from integers to some strings.
 * This would normally be some database lookup to get an object or array from
 * a key.
 *
 * @param $id
 *
 * @return
 *   The string to which the integer key mapped, or NULL if it did not map.
 */
function _menu_example_mappings($id) {
  $mapped_value = NULL;
  static $mappings = array(
    1 => 'one',
    2 => 'two',
    3 => 'three',
    99 => 'jackpot! default',
  );
  if (isset($mappings[$id])) {
    $mapped_value = $mappings[$id];
  }
  return $mapped_value;
}

/**
 * The special _load function to load menu_example.
 *
 * Given an integer $id, load the string that should be associated with it.
 * Normally this load function would return an array or object with more
 * information.
 *
 * @param $id
 *   The integer to load.
 *
 * @return
 *   A string loaded from the integer.
 */
function menu_example_id_load($id) {

  // Just map a magic value here. Normally this would load some more complex
  // object from the database or other context.
  $mapped_value = _menu_example_mappings($id);
  if (!empty($mapped_value)) {
    return t('Loaded value was %loaded', array(
      '%loaded' => $mapped_value,
    ));
  }
  else {
    return t('Sorry, the id %id was not found to be loaded', array(
      '%id' => $id,
    ));
  }
}

/**
 * Implements hook_menu_alter().
 *
 * Changes the path 'menu_example/menu_original_path' to 'menu_example/menu_altered_path'.
 * Changes the title callback of the 'user/UID' menu item.
 *
 * Remember that hook_menu_alter() only runs at menu_rebuild() time, not every
 * time the page is built, so this typically happens only at cache clear time.
 *
 * @param $items
 *   The complete list of menu router items ready to be written to the
 *   menu_router table.
 */
function menu_example_menu_alter(&$items) {

  // Change the path 'menu_example/menu_original_path' to 'menu_example/menu_altered_path'. This change will
  // prevent the page from appearing at the original path (since the item is being unset).
  // You will need to go to menu_example/menu_altered_path manually to see the page.
  if (!empty($items['menu_example/menu_original_path'])) {
    $items['menu_example/menu_altered_path'] = $items['menu_example/menu_original_path'];
    $items['menu_example/menu_altered_path']['title'] = 'Menu item altered by hook_menu_alter()';
    unset($items['menu_example/menu_original_path']);
  }

  // Here we will change the title callback to our own function, changing the
  // 'user' link from the traditional to always being "username's account".
  if (!empty($items['user/%user_uid_optional'])) {
    $items['user/%user_uid_optional']['title callback'] = 'menu_example_user_page_title';
  }
}

/**
 * Title callback to rewrite the '/user' menu link.
 *
 * @param $base_string
 *   string to be prepended to current user's name.
 */
function _menu_example_simple_title_callback($base_string) {
  global $user;
  $username = !empty($user->name) ? $user->name : t('anonymous');
  return $base_string . ' ' . $username;
}

/**
 * Title callback to rename the title dynamically.
 *
 * @param $account
 *   User account related to the visited page.
 */
function menu_example_user_page_title($account) {
  return t("@name's account", array(
    '@name' => $account->name,
  ));
}

/**
 * Implements hook_menu_link_alter().
 *
 * This code will get the chance to alter a menu link when it is being saved
 * in the menu interface at admin/build/menu. Whatever we do here overrides
 * anything the user/administrator might have been trying to do.
 *
 * @param $item
 *   The menu item being saved.
 * @param $menu
 *   The entire menu router table.
 */
function menu_example_menu_link_alter(&$item, $menu) {

  // Force the link title to remain 'Clear Cache' no matter what the admin
  // does with the web interface.
  if ($item['link_path'] == 'devel/cache/clear') {
    $item['link_title'] = 'Clear Cache';
  }
}

/**
 * Load an item based on its $id.
 *
 * In this case we're just creating a more extensive string. In a real example
 * we would load or create some type of object.
 *
 * @param $id
 */
function menu_example_arg_optional_load($id) {
  $mapped_value = _menu_example_mappings($id);
  if (!empty($mapped_value)) {
    return t('Loaded value was %loaded', array(
      '%loaded' => $mapped_value,
    ));
  }
  else {
    return t('Sorry, the id %id was not found to be loaded', array(
      '%id' => $id,
    ));
  }
}

/**
 * A to_arg() function is used to provide a default for the arg in the
 * wildcard. The purpose is to provide a menu link that will function if no
 * argument is given. For example, in the case of the menu item
 * 'menu_example/default_arg/%menu_example_arg_optional' the third argument
 * is required, and the menu system cannot make a menu link using this path
 * since it contains a placeholder. However, when the to_arg() function is
 * provided, the menu system will create a menu link pointing to the path
 * which would be created with the to_arg() function filling in the
 * %menu_example_arg_optional.
 *
 * @param $arg
 *   The arg (URL fragment) to be tested.
 */
function menu_example_arg_optional_to_arg($arg) {

  // If our argument is not provided, give a default of 99.
  return empty($arg) || $arg == '%' ? 99 : $arg;
}

/**
 * @} End of "defgroup menu_example".
 */

Functions

Name	Description
menu_example_arg_optional_load	Load an item based on its $id.
menu_example_arg_optional_to_arg	A to_arg() function is used to provide a default for the arg in the wildcard. The purpose is to provide a menu link that will function if no argument is given. For example, in the case of the menu…
menu_example_id_load	The special _load function to load menu_example.
menu_example_menu	Implementatation of hook_menu().
menu_example_menu_alter	Implements hook_menu_alter().
menu_example_menu_link_alter	Implements hook_menu_link_alter().
menu_example_perm	Implements hook_perm() to provide a demonstration access string.
menu_example_user_page_title	Title callback to rename the title dynamically.
_menu_example_basic_instructions	Page callback for the simplest introduction menu entry.
_menu_example_mappings	Utility function to provide mappings from integers to some strings. This would normally be some database lookup to get an object or array from a key.
_menu_example_menu_page	Page callback for use with most of the menu entries. The arguments it receives determine what it outputs.
_menu_example_simple_title_callback	Title callback to rewrite the '/user' menu link.