Manipulating the Drupal Breadcrumb

Drupal
is by far my favorite CMS, despite the PHP (or poohp as I tend to pronounce it). One of the places Drupal is strong is organization, as long as you want to organize everything in a web. It does provide hierarchies and has breadcrumbs, but these are where Drupal begins to show weakness. In this articles, I'm going to explore how Drupal organizes itself and how you can take advantage of that organization out of the box, or with some module help, or by custom hacking. It's a summary of the research I've been doing on the topic.

Organization

Organization of content in Drupal, as shipped, primarily operates in these ways:

• Follow that term. You click on a post in a list and see a list of categories (formally "terms" in Drupalese) associated with the post. You click on one of those and you can see all the other posts on the site that are like that one.
• Order from the menu. You can assign a page to one or more menus, which are just hierarchical lists of links. If a menu item on the screen matches what you're looking for, clicking on it will take you to the node, term page, a list, or whatever the link points to.
• By the book. Pages can be arranged in ordered hierarchies, like books. If you look at a page in one of these organizations, you can click on the sub-pages or go to the previous page or the next page or up to the next level from any page here.
• Follow that forum. Forums are really glorified category terms.

That's it. Those are all the organization options you have built-in.

Caveat Emptor

However, there are some inherent gotchas that newbies aren't always aware of. The first is that the breadcrumb is pretty weak in Drupal without some help. This usually reveals itself in a scenario like this (this is approximately how I ran into it). A newby downloads and installs Drupal, logs in as administrator, and goes to create his first vocabulary (a custom system of categories). He creates a hierarchy and adds a bunch of terms. He finishes and adds a test node that has one of the category terms set that has two or three parents. Let's say, "Food > Fruit > Citrus > Orange". However, rather than seeing a breadcrumb on the node view that reads "Home > Food > Fruit > Citrus > Orange", he just sees "Home". If he's like me, he's confused but just assumes he did something wrong. He tries clicking on the "Orange" term to see the breadcrumb there. The breadcrumb turns out to be exactly as expected, "Home > Food > Fruit > Citrus". That means if someone gets that term and clicks on the test node, the breadcrumb that should, intuitively, expand one level deeper completely evaporates.

The problem is that this is a misunderstanding of the purpose of the taxonomy system. The taxonomy system does not provide any structure for the nodes. It provides some structure for itself, but the nodes themselves still belong at the top. It's a completely flat structure. Structure is provided to nodes in Drupal core in one of two ways: the Book module and the Menu module. Which way is appropriate for your site will depend on your needs. Also, neither of these may be satisfactory, but we'll get to that in a bit.

Book Solution

The first mechanism provided by Drupal is the book module. This module allows any node to have a parent. To use the book module, you must first enable the module, configure the permissions, and then create a Book page. The first Book page will be at the "Top Level" meaning it starts a new "book". You can then create additional nodes that are in the tree. The top must always be a Book page node type, but the rest can be any node type you like, but you have to go through the extra step of configuring the node via the Outline tab after your create it. Update April 21 @ 7:28pm: I just realized this is an error. I forgot about the Outline tab. You can make any page the root of a book via the Outline tab. (Book pages automatically have the "Parent" option configured on their create form.)

If you look a the breadcrumbs of Book pages, they operate exactly as expected. Each breadcrumb is created by traversing the list of parents until it gets to the top level and then adds "Home" in front of everything. The book module can also provide a hierarchical list of pages that looks like a typical Drupal menu as well via the Book block that comes with the Book module.

This is, by far, the most common sense method for hierarchically organizing your site's content. However, if you need special content other than the book pages you have an extra step to make it work. If you need to organize non-node content (special forms or something) the Book module may not be any help at all. Also, a single node can't belong to multiple books. A node may only have 0 or 1 parents in a simple hierarchy.

Menu Solution

An even more flexible solution is through the Menu module. The Menu module allows you to create Menus, which are hierarchical lists of links (it allows you to manipulate the built-in menu items as well, but that's another topic). These links may be to nodes, terms, or anything else on the local site that has a URL. They may also be absolute links to get to locations on other web sites. Each menu item has exactly one parent, but since you're only creating links, you could have a single node or other item linked in as many different menus as you need.

Furthermore, creating a hierarchical menu also tweaks the breadcrumb. If you have a node that would otherwise appear at the top level (i.e., it doesn't belong to a book), the first menu it is listed in will be used to create a breadcrumb for that node. Therefore, if you had a taxonomy structure with a matching menu, you could fix the problem of having your node appear without a breadcrumb.

Unfortunately, this too comes at a certain cost. You must maintain the menu structure manually. You have to add each node as it goes. If you have a taxonomy structure to mimic, you have to do double duty on your data entry and then make sure your menus point to each new node you create.

Setting up the menu while creating a node is pretty easy for an administrator. Anyone with permission to administer the menus can setup the menu for a new node via the "Menu settings" box on the create page. However, if you want authors to be able to do this without being able to tweak the entire menu structure, you're out of luck. You either grant someone the right to manipulate everything or nothing, which isn't acceptable in many situations with more than a few authors.

You can address this issue by looking into the Menu Subtree Permissions
module. This allows you to grant edit access on parts of menus to certain roles.

Add-ons

There are many, many add-on solutions for handling this. I'm going to give my favorite choices and then list the others I've found. This is not a complete list, but it does highlight the modules I've examined a bit in my search for a solution.

Taxonomy Menu

A solution that uses the combined power of taxonomy and menu is available in the Taxonomy Menu
module. This module creates a menu item for each taxonomy term in the system. This automatically gives you both downward navigation through menu items and upward navigation through breadcrumbs. This isn't quite as good as the navigation provided by the book module, but with intelligent use of the sticky flag or manual items, you can come relatively close.

Add on Custom Breadcrumb

Another way of handling the breadcrumb is via the Custom Breadcrumb
module. This module allows you to associate a breadcrumb with a node based upon it's node type. For example, if you have event nodes that always needed to appear in "Home > News > Calendar > Events," then you can use the Custom Breadcrumb module to do this. If you need a more variable structure than this, then Custom Breadcrumb still doesn't do it.

Others

Here are some other add-on modules that you may wish to consider:

• Taxonomy Bradcrumb
  . This module provides half the abilities of the Taxonomy Menu in tweaking the breadcrumb. It does not, however, provide any way to navigate down to the items in the tree, just the parents on the way back up.
• Category
  . For the daring, there's also the Category
  module which provides a complete replacement system for the core Taxonomy module, Book module, and provides a special menu module for creating menu items automatically on the creation of nodes. However, this is a big module with lots of options and I've back off from using it because it's almost too powerful to figure out how to use it most effectively. I've had some trouble getting it to work really well.
• Pathauto
  . This module doesn't actually help you organize your site, but it can makes your URLs match your breadcrumb organization structure. I highly recommend this module to make your URLs pretty. However, be aware that the URL aliases can quickly clutter the URL Alias page if you have a lot of pages.

• Theme Hacks

  If you do a search on the Drupal site for "breadcrumb" you will come across several hacks to the theme. All of which are customizations that make use of drupal_set_breadcrumb()
. You pass that function an array of links and it will give that array of links to the page template. This is the ultimate solution if no other will work for you.

  However, again, this still only gives you the upward navigation. It doesn't provide any kind of downward navigational structure.

  Conclusion

  Drupal does provide ways for organizing your content, but some of the out-of-the-box methods may not be ideally suited for your situation. Drupal comes out of the box with excellent support for web-like and river-of-news style organization. Hierarchies are quite possible and can be managed, but the structures provided for such assume a relatively light amount of hierarchical information. However, by using a few modules and the taxonomy structure, you can create very flexible and functional hierarchies to suit any site structure.