WordPress: Taxonomy Term Meta Drill Down With Pre_Get_Terms

wordpress-pre-get-terms

add_action( 'pre_get_terms', 'filter_pre_get_terms', 10, 2 );

/** 
* Filter WP_Term_Query meta query 
* - a better drill down for filtering term meta data 
* - keeps pagination in line with term count 
* - used in term edit page 
* 
* @param   object  $query  WP_Term_Query 
*/
function filter_pre_get_terms( $query ) {    
  
  global $pagenow;
  
  $taxonomy = filter_input( INPUT_GET, 'taxonomy', FILTER_SANITIZE_STRING );
  
  // only if current post type or edit page in admin
  if ( !is_admin() || $pagenow !== 'edit-tags.php' || !in_array( $taxonomy, [ 'taxonomy' ] ) ) { return $query; }
  
  // store current query vars
  $query_vars = $query->query_vars;
  $args = [];
  
  // test meta
  $meta = ( isset( $_GET['meta-field-name'] ) ) ? sanitize_text_field( urldecode( $_GET['meta-field-name'] ) ) : '';
  if ( empty( $meta ) ) { return; }
  
  // set meta query
  $args['meta_query'] = [
    [
      'key'       => 'meta-field-name',
      'value'     => $meta,
      'compare'   => 'LIKE'
    ]
  ];
  
  // refresh query vars
  $query->query_vars = array_merge( $query_vars, $args );
}

// Requires term meta column filter to be active and column value to be wrapped in link with '&meta-field-name=meta-field-value'