WordPress: タグ同士のつながりを可視化する

// 1 $post_query->posts = array{ post_id }
$post_query = new WP_Query( [
    'post_type'      => 'post',
    'post_status'    => 'publish', 
    'category_name'  => 'list',
    'tag_id'         => $term_id,
    'posts_per_page' => -1,
    'fields'         => 'ids',
] );

// 2 $term_query->terms = array{ term object }
$term_query = new WP_Term_Query( [ 
    'taxonomy'               => 'post_tag',
    'object_ids'             => $post_query->posts,
    'exclude'                => $term_id,
    'fields'                 => 'all_with_object_id',
    'update_term_meta_cache' => false,
] );

// 3 $postcount_by_tag = array{ term_id => postcount }
$postcount_by_tag = array_count_values( 
    array_column( $term_query->terms, 'term_id' )
);

// 4 $related_tags = array{ term_id => term object (w/postcount) }
foreach ( $term_query->terms as $term ) {
    if ( ! isset( $related_tags[$term->term_id] ) ) {
        $term->postcount = $postcount_by_tag[$term->term_id];
        $related_tags[$term->term_id] = $term;
    }
}

// 5
usort( $related_tags, function( $a, $b ) {
    if( 0 === $ret = $b->postcount - $a->postcount ) {
        $ret = $b->count - $a->count;
    }
    return $ret;
} );

// 1
array_walk( $related_tags, function( &$term, $key ){
    $term->link = get_term_link( $term, 'post_tag' );
    $term->id   = $term->term_id;
} );

// 2
add_filter( 'tag_cloud_sort', function( $tags, $args ) use( $related_tags ){
    return $related_tags;
}, 10, 2 );

// 3
$cloud = wp_generate_tag_cloud( current( $related_tags ), [
    'number'    => 0, // all
    'smallest'  => 1, 
    'largest'   => 1.6,
    'unit'      => 'em', 
    'separator' => '',
] );