WP Query: Custom Post Types and Categories

[atomicjack]

Hi,

It seems that you cannot use a custom post type's category as a filter during a WP Query, see here:

<?php
$the_query = new WP_Query('cat=4&taxonomy=product_categories&posts_per_page=-1&post_type=products&status=publish' );

						if ( $the_query->have_posts() ) {
							echo '<ul>';
							while ( $the_query->have_posts() ) {
								$the_query->the_post(); ?>
								<?php    
								$queried_objects = get_the_terms($post->ID, 'product_category');
								foreach ( $queried_objects as $queried_object ) {
									$current_term = $queried_object->term_id;
								}
								?>

Whenever a category ID is placed in to the query, no results will be returned, even though there are items in there.

[atomicjack]

Seems that, since custom post types were added, this area of WordPress has been left a little untouched.

Allow me to explain, after a bit of research (and discussing with some guys at work), the issue lies around WordPress v3.

Custom Post Types don't use the normal default category system, they use, essentially, a custom category, now, expected behaviour would be that the "cat=" parameter would work, because the system is still only looking for one type of category.

However - as this area has been left untouched, that's not the case, and instead we have to do something much longer, like:

					<?php
					$args = array(
	'post_type' => 'products',
	'tax_query' => array(
		array(
			'taxonomy' => 'product_category',
			'field'    => 'example',
			'terms'    => 'bob',
		),
	),
);
$query = new WP_Query( $args );
					?>

I think we need to get this changed, so that, if it is a custom post type, the cat= will look for the categories within that post type.

[swissspidy]

I think we need to get this changed, so that, if it is a custom post type, the cat= will look for the categories within that post type.

This would majorly break backwards compatibility.

The docs are very clear that cat is a category (built-in taxonomy category) parameter. Just like that, tag is a tag (built-in taxonomy post_tag) parameter.

Custom post types usually use custom taxonomies. Category is just one taxonomy, terms is another. Developers are encouraged to use tax_query for queries involving custom taxonomies rather than mis-using cat and tag for something they aren't intended for. Even if that means more typing.

[boonebgorges]

As noted by swissspidy, this seems to be a misunderstanding of terminology. 'cat' is short for 'category'. 'category' is a specific taxonomy. When you register a custom taxonomy 'product_category', this is *not* the same as a WP 'category'. The two are siblings (they're both types of taxonomies); 'product_category' is not a type of category.

I do recommend full WP_Tax_Query syntax in your code, for clarity. However, you can also use the following shorthand:

'product_category=foo,bar&...'

where 'foo' and 'bar' are the slugs of terms in your 'product_categories' taxonomy.

Thanks for the ticket!