Creating a Custom Taxonomy

Editing your theme’s functions.php file

WordPress version 3 does not allow you to create custom taxonomies from the administration screen. To initially define your custom taxonomies without a plugin, you’ll need to add a little bit of code to your theme’s functions.php file. This isn’t too difficult — just follow my lead.

To add custom taxonomies, we need to edit the “functions.php” file found inside your theme directory. Location of functions.php :  [website_root]/wp/wp-content/themes/[your_theme]/functions.php

Adding the Taxonomies in Code

1. One Function to Create Them All

   First, we need to build one function that creates all the taxonomies we need. We’ll call the function “build_taxonomies.” Let’s add this function to the bottom of the functions.php file.

   <?php
      function build_taxonomies() {
   	// code will go here
   	}
   ?>
   

2. Defining the Taxonomies

   Next, for each taxonomy we want to create, we need to call a particular WordPress function with the right parameters. Here’s the function, and its important parameters explained.

   <?php
     register_taxonomy(
       'internal_name',
       'object_type',
       array(
         'hierarchical' => {true|false},
         'label' => 'Human Readable Name',
         'query_var' => {true|false},
         'rewrite' => {true|false}
       )
    );
   ?>
   

   • internal_name: What will this taxonomy be called from inside WordPress, in the database and template files?
   • object_type: Which types of content can be classified with this taxonomy? Possible values are “post, page, link,” and then names of custom post types we’ll learn to create in a future tutorial.
   • Next comes an array of optional parameters. We’ll use the most important ones here in this tutorial, but a full list can be found on the Function Reference / register_taxonomy Codex page. The parameters we’ll use are:
   • hierarchical: If ‘true,’ this taxonomy has hierarchical abilities like WordPress Categories. If ‘false,’ this taxonomy behaves much like freeform Tags.
   • label: This is the human-readable name used in your site’s interface to label the taxonomy.
   • query_var: If ‘true,’ we’ll be able to ask WordPress for posts dependent upon the selections for this taxonomy. For example, we could search for all the posts where the operating system taxonomy has ‘Windows’ selected.
   • rewrite: If ‘true,’ WordPress will use friendly URL’s when viewing a page for this taxonomy. For example, a page listing all the posts with the “Windows” operating system selected would be represented by the following url: http://domain.com/operating_system/windowsOur entry specific to adding the Operating System taxonomy looks like so:

     <?php
     register_taxonomy( 'operating_system', 'post', array( 'hierarchical' => true,
     'label' => 'Operating System',
     'query_var' => true,
     'rewrite' => true )
     );
     ?>
     

3. Calling the Taxonomy-Creating Function

   We need to add one more line to the “functions.php” file so our “build_taxonomies” function will actually be executed. We’ll “hook” the “build_taxonomies” function to the “init” event by adding the following code:

   add_action( 'init', 'build_taxonomies', 0 );
   

   You can add this line anywhere, but I generally add it above the function we’re calling, so it would look like this:

   <?php
       // Custom Taxonomy Code
       add_action( 'init', 'build_taxonomies', 0 );
   
       function build_taxonomies() {
         register_taxonomy( 'operating_system', 'post', array( 'hierarchical' => true, 'label' => 'Operating System', 'query_var' => true, 'rewrite' => true ) );
       }
   ?>
   

More Information

register_texonomy

Hope it will help to all. Try this on your blog.