Custom Taxonomy Filter in WordPress Admin

If you have a lot of custom posts on your website, then sometimes it would be much easier to filter them by a specific taxonomy when you manage them in your WordPress admin.

Yes, search is also ok, but maybe a taxonomy filter will be just what you need? Here is how it is going to look like in WordPress admin:

Below is the code that allows to add a taxonomy filter for a specific taxonomy:

<?php
add_action( 'restrict_manage_posts', 'rudr_taxonomy_filter' );

function rudr_taxonomy_filter( $post_type ) {

	// do nothing it it is not a post type we need
	if( 'lesson' !== $post_type ) {
		return;
	}
	
	$taxonomy_name = 'course_category';

	// get all terms of a specific taxonomy
	$courses = get_terms( 
		array( 
			'taxonomy' => $taxonomy_name, 
			'hide_empty' => false
		)
	);
	// selected taxonomy from URL
	$selected = isset( $_GET[ $taxonomy_name ] ) && $_GET[ $taxonomy_name ] ? $_GET[ $taxonomy_name ] : '';
	
	if( $courses ) {
		?>
			<select name="<?php echo $taxonomy_name ?>">
				<option value="">All courses</option>
				<?php
					foreach ( $courses as $course ) {
						?><option value="<?php echo $course->slug ?>"<?php selected( $selected, $course->slug ) ?>><?php echo $course->name ?></option><?php
					}
				?>
			</select>
		<?php
	}
}

What is worth to keep in mind here:

• I used $post_type argument of the function in order to make a condition, so the filter will be displayed only for a specific post type. But this argument is available only since WordPress 4.4, so if you’re using an older version of WP, please use global $typenow instead.
• If you do not know where to insert the code, please read this tutorial.
• Please take a look at line 26, the string “All courses” can also be printed dynamically, for example: $taxonomy->labels->all_items but of course you have to get a taxonomy object first with $taxonomy = get_taxonomy( $taxonomy_name ).

And also it is possible to simplify the filter by changing HTML to wp_dropdown_categories() and why not let’s extend it to multiple taxonomies.

add_action( 'restrict_manage_posts', 'rudr_taxonomy_filter' );

function rudr_taxonomy_filter( $post_type ){
	
	// let's decide about post type first
	if( 'my_post_type' !== $post_type ){
		return;
	}
	// pass multiple taxonomies as an array of their slugs
	$taxonomies = array( 'taxonomy_1', 'taxonomy_2' );
	
	// for every taxonomy we are going to do the same
	foreach( $taxonomies as $taxonomy ){
		
		$taxonomy_object = get_taxonomy( $taxonomy );
		$selected = isset( $_GET[ $taxonomy ] ) ? $_GET[ $taxonomy ] : '';
		
		wp_dropdown_categories( 
			array(
				'show_option_all' =>  $taxonomy_object->labels->all_items,
				'taxonomy'        =>  $taxonomy,
				'name'            =>  $taxonomy,
				'orderby'         =>  'name', // slug / count / term_order etc
				'value_field'     =>  'slug',
				'selected'        =>  $selected,
				'hierarchical'    =>  true,
			)
		);
	}
}

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Misha Rudrastyh

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