WordPress: Taxonomy Meta Sorting With Terms_Clauses Filter

wordpress_terms_clauses_sorting.txt

add_filter( 'terms_clauses', 'filter_terms_clauses', 10, 3 );
/** 
* Filter WP_Term_Query meta query 
* 
* @param   object  $query  WP_Term_Query 
* @return  object 
*/
function filter_terms_clauses( $pieces, $taxonomies, $args ) {
    
    global $pagenow, $wpdb;     
    
    // Require ordering    
    $orderby = ( isset( $_GET['orderby'] ) ) ? trim( sanitize_text_field( $_GET['orderby'] ) ) : '';     
    if ( empty( $orderby ) ) { return $pieces; }    
    
    // set taxonomy    
    $taxonomy = $taxonomies[0];    
    
    // only if current taxnomy or edit page in admin        
    if ( !is_admin() || $pagenow !== 'edit-tags.php' || !in_array( $taxonomy, [ 'my-taxonomy-name' ] ) ) { return $pieces; }    
    
    // and ordering matches
    if ( $orderby === 'my-taxonomy-meta-field-name' ) {        
        $pieces['join']  .= ' INNER JOIN ' . $wpdb->termmeta . ' AS tm ON t.term_id = tm.term_id ';        
        $pieces['where'] .= ' AND tm.meta_key = "my-taxonomy-meta-field-name" ';         
        $pieces['orderby']  = ' ORDER BY tm.meta_value ';     
    }    
    
    return $pieces;
}

// Change taxonomy and taxonomy meta fields as required. Requires taxonomy meta column and sortable column filters to be active. 
// This just ties them together and makes the taxonomy meta field column sortable