您可以在每次需要时编写一个简单的函数来执行此操作。下面是我在上找到的一个示例this website.

function pa_category_top_parent_id( $catid ) {
    while( $catid ) {
        $cat = get_category( $catid ); // get the object for the catid
        $catid = $cat->category_parent; // assign parent ID (if exists) to $catid
        // the while loop will continue whilst there is a $catid
        // when there is no longer a parent $catid will be NULL so we can assign our $catParent
        $catParent = $cat->cat_ID;
    }
    return $catParent;
}

$catid = get_query_var( \'cat\' );
echo pa_category_top_parent_id( $catid );