custom field post value replace wordpress post title
add_action( 'acf/save_post', 'biwp_set_title_from_first_last_name', 20 );
function biwp_set_title_from_first_last_name( $post_id ) {
$post_type = get_post_type( $post_id );
if ( 'contributor' == $post_type ) {
$first_name = get_field( 'biwp_first_name', $post_id );
$last_name = get_field( 'biwp_last_name', $post_id );
$title = $first_name . ' ' . $last_name;
$data = array(
'ID' => $post_id,
'post_title' => $title,
'post_name' => sanitize_title( $title ),
);
wp_update_post( $data );
}
}