See: Automatically display titles on Category and Tag Archives
<?php
/**
* Default Titles for Term Archives
*
* @author Bill Erickson
* @see https://www.billerickson.net/default-category-and-tag-titles
*
* @param string $value
* @param int $term_id
* @param string $meta_key
* @param bool $single
* @return string $vlaue
*/
function ea_default_term_title( $value, $term_id, $meta_key, $single ) {
if( ( is_category() || is_tag() || is_tax() ) && 'headline' == $meta_key && ! is_admin() ) {
// Grab the current value, be sure to remove and re-add the hook to avoid infinite loops
remove_action( 'get_term_metadata', 'ea_default_term_title', 10 );
$value = get_term_meta( $term_id, 'headline', true );
add_action( 'get_term_metadata', 'ea_default_term_title', 10, 4 );
// Use term name if empty
if( empty( $value ) ) {
$term = get_queried_object();
$value = $term->name;
}
}
return $value;
}
add_filter( 'get_term_metadata', 'ea_default_term_title', 10, 4 );