Matching Single-Entry Categories to Channel Categories

Hi EE forums,

I’m looking for a more elegant way to accomplish the following inside of a single-entry page:

1. Dynamically list all of the categories for the channel.
2. Mark any categories that the entry is filed under as “selected.”
3. Mark every other list item as “odd” (e.g. items 1, 3, 5, etc.). This is potentially a separate issue (see below).

Keep in mind that each channel entry is filed under multiple (parent-level) categories and there is no category segment to reference in the URL. I will eventually employ a plugin solution as to avoid using PHP inside the template, however, I’m looking to get some feedback on this approach first:

Code

<ul>

 <?php
  $i = 0;

  // get the classes for the category
  function get_category_classes($index, $channel_category, $indexClass = 'odd', $activeClass = 'selected')
  {
   $classes = array();
   $output  = '';

   // is the iterator an odd number?
   if ($index % 2 == 0) array_push($classes, $indexClass);

   // does the channel category match any of the entry categories?
   $entry_categories = explode(' ', '{categories}{category_name} {/categories}');
   if (in_array($channel_category, $entry_categories)) array_push($classes, $activeClass);

   // format the output (e.g. class="odd selected" or class="odd")
   if ( ! empty($classes)) $output = ' class="'.trim(implode(' ', $classes)).'"';

   return $output;
  }
 ?>

 {exp:channel:categories channel="blog" style="linear"}
 <li<?= get_category_classes($i, '{category_name}') ?>>
  <a href="http://{path=blog}">{category_name}</a>
 </li>
 <?php $i++ ?>
 {/exp:channel:categories}

</ul>

With respect to using an iterator to mark list items as “odd”: my first inclination was to use the {switch='odd|even'} tag. Sadly, this tag does not work correctly inside {exp:channel:categories} (e.g. it will return “odd” for every item). This is a known limitation, correct?

EE Info

Version: 2.4.0
Build: 20120123