if ( ! is_admin() ) {
add_filter( \'wp_get_nav_menu_items\', \'display_last_posts_for_menu_item_ts\', 10, 3 );
}

function display_last_posts_for_menu_item_ts( $items, $menu, $args ) { 
    $menu_order = count($items); /* Offset menu order */
    $post_ids = array(250,973);
    $args = array ( \'include\' => $post_ids );
    $child_items = array();
    foreach ( $items as $item ) {        
        foreach ( get_posts( $args ) as $post ) {
            // Add sub menu item
            $img = get_the_post_thumbnail ( $post->id, \'thumbnail\' );
            $post_thumbnail_id = get_post_thumbnail_id( $post->id );
            $img .= \'<!--\' . $post_thumbnail_id . \' / \' . $post->ID . \'-->\';
            $post->menu_item_parent = $item->ID;
            $post->post_type = \'nav_menu_item\';
            $post->object = \'custom\';
            $post->type = \'custom\';
            $post->menu_order = ++$menu_order;
            $post->title = $img . $post->post_title;
            $post->url = get_permalink( $post->ID );
            /* add children */
            $child_items[]= $post;
        } 
    }
    return array_merge( $items, $child_items );
}

我正在使用此功能添加子菜单（修改自Category menu item and its last 10 posts as sub-menu ). 出于我无法理解的原因，我无法获取这些帖子的缩略图-尽管超出了此功能get_the_post_thumbnail ( 973, \'thumbnail\' ); 返回预期结果。有什么想法吗？

$img = get_the_post_thumbnail ( $post->id, \'thumbnail\' ); 

$img = get_the_post_thumbnail ( $post, \'thumbnail\' );