Red Leaf Media

Drupal has many great contributed modules that make it perhaps the most flexible open source CMS around.  However, I ran into a use case this summer that I didn't know how to solve with existing modules.

One of my current clients is NYC-based Brick Underground.  In the most basic sense this site is a blog that covers a broad range of topics related to NYC living.  Drupal's core taxonomy system is used tag blog entries.  As part of a recent upgrade the site owner wanted to have a "hot topic" list which would include tags that were hand-chosen by editors.  I was already familiar with the nodequeue module, which allows editors to hand pick nodes into arbitraty listings, but I was unaware of any way to achieve a similar outcome with taxonomy terms.  Thankfully Drupal's modular framework provides the ability for a developer to add in custom capabilities like hot topic lists.  As such, I set out to write the functionality myself.

***NOTE: This work is all relevant to Drupal 6.  Bits and pieces may apply to other versions, but mileage may vary.***

I first must decide what information I need to store and exactly how I will go about storing/retrieving it.  At the most basic level, I simply need to store the id numbers ("tid" values) of each tag that the editors have designated as "hot topics".  The simplest way to store these tid values is a single comma-separated string of numbers (e.g. "1,2,5,8").  I will edit and retrieve this string of tid values using Drupal's variable_get() and variable_set() functions, which utilize the "variable" table in the Drupal database.

Let's say that I call the custom module "Hot Topics" and use the string "hot_topics" for the module directory and filenames.  I need to create a directory with the name "hot_topics" in the "sites/all/modules" directory.  Within that directory I will create a file named "hot_topics.info":

Then I will create a "hot_topics.module" file which contains all of the actual code to perform the desired task.  I start by setting up the hot topics administration page using Drupal's hook_menu() function:

This is telling Drupal that I want a page at "http://mysite.com/admin/settings/hot_topics" for the admin page. Only users with the "administer taxonomy" permission can access the page, which seems logical. The function hot_topics_page() defines the page's contents: function hot_topics_page(){ return drupal_get_form('hot_topics_settings_form'); } This tells Drupal to obtain a form named "hot_topics_settings_form" and return that form as the page's contents.  This form is defined as follows (with inline comments to help explain):

This sets up a form that contains checkboxes for all of the site's taxonomy terms. They are divided into their respective vocabularies to make the form easier to understand on a site that has many vocabularies. The variable 'hot_topics_terms' is used to check any boxes that have previously been checked by the administrators.

Next I must setup a function that handles submission of the form, hot_topics_settings_form_submit():

This basically takes the checked terms and serializes their tid values and saves that string to the 'hot_topics_terms' variable in the database.

Now I need a simple way to output the selected hot topics as a list, for display in a Drupal block. This is done using hook_block:

This tells Drupal that my module outputs a single block. That block uses the function hot_topics_block_contents() to obtain its contents:

That should do the trick. It's a basic system that allows administrators to hand pick taxonomy terms to be "hot topics". The selected terms are then output as a basic item list in a block.