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CHAPTER 4 ■ THE MENU SYSTEM
'access callback' => TRUE, 'type' => MENU_NORMAL_ITEM, 'weight' => -10
);
return $items;
}
function menufun_hello($animal) { return t(“Hello $animal”);
}
function a_zoo_animal_to_arg($arg) {
//$arg is '%' since it is a wildcard
//Let's replace it with a zoo animal. return 'tiger';
}
This causes the link “Hi” to appear in the navigation block. The URL for the link is http://example.com/?q=menufun/tiger. Normally, you would not replace the wildcard with a static string as in this simple example. Rather, the to_arg() function would produce something dynamic, like the uid of the current user or the nid of the current node.
Altering Menu Items from Other Modules
When Drupal rebuilds the menu_router table and updates the menu_link tables (for example, when a new module is enabled), modules are given a chance to change any menu item by implementing hook_menu_alter(). For example, the “Log off” menu item logs out the current user by calling user_logout(), which destroys the user’s session and then redirects the user to the site’s home page. The user_logout() function lives in modules/user/user.pages.inc, so the menu item for the Drupal path has a file key defined. So normally Drupal loads the file modules/user/user.pages.inc and runs the user_logout() page callback when a user clicks the “Log out” link from the navigation block. Let’s change that to redirect users who are logging out to drupal.org.
/**
*Implementation of hook_menu_alter().
*@param array $items
*Menu items keyed by path.
*/
function menufun_menu_alter(&$items) {
//Replace the page callback to 'user_logout' with a call to
//our own page callback.
$items['logout']['page callback'] = 'menufun_user_logout'; $items[‘logout’][‘access callback’] = ‘user_is_logged_in’;
//Drupal no longer has to load the user.pages.inc file
//since it will be calling our menufun_user_logout(), which
//is in our module -- and that's already in scope.
unset($items['logout']['file']);
}
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CHAPTER 4 ■ THE MENU SYSTEM
/**
*Menu callback; logs the current user out, and redirects to drupal.org.
*This is a modified version of user_logout().
*/
function menufun_user_logout() { global $user;
watchdog('menufun', 'Session closed for %name.', array('%name' => $user->name));
//Destroy the current session: session_destroy();
//Run the 'logout' operation of the user hook so modules can respond
//to the logout if they want to.
module_invoke_all('user', 'logout', NULL, $user);
//Load the anonymous user so the global $user object will be correct
//on any hook_exit() implementations.
$user = drupal_anonymous_user();
drupal_goto('http://drupal.org/');
}
Before our hook_menu_alter() implementation ran, the menu item for the logout path looked like this:
array( |
|
'access callback' |
=> 'user_is_logged_in', |
'file' |
=> 'user.pages.inc', |
'module' |
=> 'user', |
'page callback' |
=> 'user_logout', |
'title' |
=> 'Log out', |
'weight' |
=> 10, |
) |
|
And after we have altered it, the page callback is now set to menufun_user_logout:
array( |
|
'access callback' |
=> 'user_is_logged_in', |
'module' |
=> 'user', |
'page callback' |
=> 'menufun_user_logout', |
'title' |
=> 'Log out', |
'weight' |
=> 10, |
) |
|
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CHAPTER 4 ■ THE MENU SYSTEM
Altering Menu Links from Other Modules
When Drupal saves a menu item to the menu_link table, modules are given a chance to change the link by implementing hook_menu_link_alter(). Here is how the “Log out” menu item could be changed to be titled “Sign off.”
/**
*Implements hook_menu_link_alter().
*@param $item
*Associative array defining a menu link as passed into menu_link_save()
*/
function menufun_menu_link_alter(&$item) { if ($item['link_path'] == 'user/logout') {
$item['link_title'] = 'Sign off';
}
}
This hook should be used to modify the title or weight of a link. If you need to modify other properties of a menu item, such as the access callback, use hook_menu_alter() instead.
■ Note The changes made to a menu item in hook_menu_link_alter() are not overrideable by the user interface that menu.module presents at Administer -> Site building -> Menus.
Kinds of Menu Items
When you are adding a menu item in the menu hook, one of the possible keys you can use is the type. If you do not define a type, the default type MENU_NORMAL_ITEM will be used. Drupal will treat your menu item differently according to the type you assign. Each menu item type is composed of a series of flags, or attributes (see includes/menu.inc). Table 4-3 lists the menu item type flags.
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CHAPTER 4 ■ THE MENU SYSTEM
Table 4-3. Menu Item Type Flags |
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Binary |
Hexadecimal |
Decimal |
Constant |
Description |
|
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|
|
|
|
|
000000000001 |
0x00 |
01 |
1 |
MENU_IS_ROOT |
Menu item is the root of |
|
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|
|
|
the menu tree |
000000000010 |
0x00 |
02 |
2 |
MENU_VISIBLE_IN_TREE |
Menu item is visible in the |
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|
|
|
menu tree |
000000000100 |
0x00 |
04 |
4MENU_VISIBLE_IN_BREADCRUMB |
Menu item is visible in the |
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|
breadcrumb |
000000001000 |
0x00 |
08 |
8MENU_LINKS_TO_PARENT |
Menu item links back to |
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|
|
its parent |
000000100000 |
0x00 |
20 |
32 |
MENU_MODIFIED_BY_ADMIN |
Menu item can be |
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|
|
modified by administrator |
000001000000 |
0x00 |
40 |
64 |
MENU_CREATED_BY_ADMIN |
Menu item was created by |
|
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|
|
|
administrator |
000010000000 |
0x00 |
80 |
128 |
MENU_IS_LOCAL_TASK |
Menu item is a local task |
000100000000 |
0x01 |
00 |
256 |
MENU_IS_LOCAL_ACTION |
Menu item is a local |
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|
action |
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|
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|
For example, the constant MENU_NORMAL_ITEM (define('MENU_NORMAL_ITEM', MENU_VISIBLE_IN_TREE | MENU_VISIBLE_IN_BREADCRUMB) has the flags MENU_VISIBLE_IN_TREE and MENU_VISIBLE_IN_BREADCRUMB, as shown in Table 4-4.
Table 4-4. Flags of the Menu Item Type MENU_NORMAL_ITEM
Binary |
Constant |
|
|
000000000010 MENU_VISIBLE_IN_TREE
000000000100 MENU_VISIBLE_IN_BREADCRUMB
000000000110 MENU_NORMAL_ITEM
Therefore, MENU_NORMAL_ITEM has the following flags: 000000000110. Table 4-5 shows the available menu item types and the flags they express.
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