我正在尝试在RSS输出中测试帖子类别，但是in\\u category（）或has\\u category（）函数都将失败。“手动”测试类别将起作用。我错过了什么？

    add_filter( "the_content_feed", "RSS_my_filter" );

    function RSS_my_filter($content){
    global $post;
    if (has_category(\'Class Blog\', $post-ID)){
        // FAILS!!!!  
        $content = \'***************\';
    }
    $categories_list = get_the_category( $post->ID );
    foreach ($categories_list as $category) {
         if($category->name == \'Class Blog\'){
            // WORKS 
            $content = \'***************\';
        }
    }
    return $content;
    }