Perhaps you’ve been here before: you want to show all of the categories in a particular ExpressionEngine category group, while also highlighting only those categories to which a particular entry belongs.

This is not something EE’s category tags can do natively, so I set out to find a way. I’ll show you what I discovered in this short tutorial.

Last things first: the final result

In case the concept is still abstract, here is a screenshot of the final result:

A list of all categories, with active ones checked

What you see is a portion of a Safecracker form for editing a single entry. I wanted to let the end user see all of the category options, as well as which categories were already selected for the current entry. A checkbox field seemed like a logical choice.

You’ll notice that some of the checkboxes are checked, and that there are no duplicate categories. I know…like magic.

How it’s done

In this example, I’m using an embedded template, but that may not be necessary for everyone. In your parent template, place the following code:

<h2>Type of Venue</h2>
<div class="cats">{embed="includes/fetch_cats" cat_group="1" entry_id="{entry_id}"}</div>

Then, in your embedded template (includes/fetch_cats in this example), place the following code:

<?php
// get all categories in the specified group
$all_cats = $this->EE->db->query ( "SELECT cat_id, cat_name FROM exp_categories WHERE group_id = '{embed:cat_group}' ORDER BY cat_name" );

// loop through each cat returned, marking a box checked if the current entry is in that cat
foreach ( $all_cats->result() as $row ) {
   $venue_cats = $this->EE->db->query ( "SELECT cat_id AS venue_cat_id FROM exp_category_posts WHERE entry_id='{embed:entry_id}' AND cat_id = '" . $row->cat_id . "'" );
   if ( $venue_cats->num_rows() ) {
      echo '<label><input checked="checked" type="checkbox" name="category[]" value="' . $row->cat_id . '" /> ' . $row->cat_name . '</label>';
   } else {
      echo '<label><input type="checkbox" name="category[]" value="' . $row->cat_id . '" /> ' . $row->cat_name . '</label>';
   }
} ?> 

Be sure that your embedded template has PHP enabled on Output.

That’s all there is to it. The nice thing about using an embedded template is that it’s very modular; you can pass any category group ID  and entry ID to it and it will return the expected categories.