Query Posts by Taxonomy

Hey all,
I’ve seen heaps of custom queries up that solve individual cases where people want to search a particular post type and filter it by a custom taxonomy and term, but nothing that was a reusable function. So I wrote one. This is far from perfect, but it suits my purposes until this sort of query is built into WP.

I’m merely putting this code out there to save someone else from doing it later. If you find a bug or have a suggestion please add it to the code and post it up here for all to use.

Just dump this code in your functions.php file and call it in place of something like get_posts().

/*-------------------------------------------------------------------
Get Posts by a Taxonomy Terms
by Benji Greig [email protected]
-------------------------------------------------------------------
This function allows for a query to be made similar to get_posts but
allows for filtering by 'taxonomy_name' and multiple taxonomy terms.

You can filter the query by comma delimited lists of:
		- 'taxonomy_terms'
		- 'post_types'

Additionally you can filter the query by 'post_status' and define
the 'orderby' from any of the posts fields and set either ascending
or decending. It's not perfect, but it's coming in real handy for
making special queries.
-------------------------------------------------------------------*/

function get_posts_by_taxonomy($args) {
	global $wpdb;
//
	if ( is_array($args) )
	  $options = &$args;
	else
	  parse_str($args, $options);
//
	$defaults = array(
		'post_type' => null,
		'post_status' => 'publish',
		'taxonomy_name' => null,
		'taxonomy_term' => null,
		'orderby' => 'post_date',
		'order' => 'DESC',
		'numberposts' => '10'
	);
	$options = array_merge($defaults, $options);
	extract($options);
//
	//Format the post_type list so that it works in the query
	$post_type = "('".str_replace(",","', '",$options['post_type'])."')";
//
	//Get the term IDs from the Term Names
	$terms = split('[,]', $options['taxonomy_term']);
	$term_ids = $options['taxonomy_term'];
	foreach($terms as $term){
		$t_data = term_exists($term, 'show-in');
		$term_ids = str_replace($term,"'".$t_data['term_id']."'",$term_ids);
	}
	$term_ids = "(".$term_ids.")";
//
	//Build the query
	$query = "SELECT $wpdb->posts.* FROM $wpdb->posts
	INNER JOIN $wpdb->term_relationships ON ($wpdb->posts.ID = $wpdb->term_relationships.object_id)
	INNER JOIN $wpdb->term_taxonomy ON ($wpdb->term_relationships.term_taxonomy_id = $wpdb->term_taxonomy.term_taxonomy_id)
	WHERE 1=1
	";
	if($options['taxonomy_name'] != null){$query .="AND $wpdb->term_taxonomy.taxonomy = '".$options['taxonomy_name']."'
	";
	if($options['taxonomy_term'] != null){$query .="AND $wpdb->term_taxonomy.term_id IN $term_ids
	";}
	}
	if($options['post_type'] != null){$query .="AND $wpdb->posts.post_type IN $post_type
	";}
	$query .="AND $wpdb->posts.post_status = '".$options['post_status']."'
	";
	$query .="GROUP BY $wpdb->posts.ID
	";
	$query .="ORDER BY $wpdb->posts.".$options['orderby']." ".$options['order'];

	$my_posts = $wpdb->get_results($query);
	return($my_posts);

}

Here is an example usage of it:

$args = array(
	'post_status' => 'publish',
	'taxonomy_name' => 'show-in',
	'taxonomy_term' => 'al-pacino, robert-de-niro'
);
$custom_posts = get_posts_by_taxonomy($args);