FacetWP - compare different facets in "OR" mode (experimental)

functions.php

<?php

add_filter( 'facetwp_filtered_post_ids', function( $post_ids, $class ) {
    if ( ! empty( FWP()->or_values ) ) {
        $post_ids = [];
        foreach ( FWP()->or_values as $facet_name => $matches ) {
            foreach ( $matches as $match ) {
                $post_ids[] = $match;
            }
        }
        $post_ids = array_unique( $post_ids );
    }
    return $post_ids;
}, 10, 2 );