试图在多站点中为管理员获取非对象的属性“ID”

Question

I'm using QAengine theme on my wordpress multisite. Here is the first part of the code used to avoid getting administrators listed within top users of the blog

function widget( $args, $instance ) {
    global $wpdb;

    $admins_id = array();
    $admins    = get_users( 'role=administrator' );
    //normal site
    if(!empty($admins)){
        foreach ($admins as $admin) {
            $admins_id[] = $admin->ID;
        }
    }
    //multisites
    if(is_multisite()){
        $super_admins = get_super_admins();
        if(!empty($super_admins)){
            foreach ($super_admins as $admin) {
                $admin       = get_user_by( 'slug', $admin );
                $admins_id[] = $admin->ID;  //$admin['ID'];
            }
        }
    }

}

I'm getting the error message "Trying to get property 'ID' of non-object" at the top of the 'top users list',which is due to $admins_id[] = $admin->ID;. Replacing $admin->ID by $admin['ID']; results in a blank page.

and this what I get for var_dump($admins)

array(1) { [0]=> object(WP_User)#5237 (8) { ["data"]=> object(stdClass)#5236 (12) { ["ID"]=> string(1) "1" ["user_login"]=> string(5) "admin" ["user_pass"]=> string(34) "$P$BByirivlLnImmFrkUwGXorARgM6yFY/" ["user_nicename"]=> string(4) "dmin" ["user_email"]=> string(27) "[e-mail]" ["user_url"]=> string(0) "" ["user_registered"]=> string(19) "2018-01-14 11:17:25" ["user_activation_key"]=> string(0) "" ["user_status"]=> string(1) "0" ["display_name"]=> string(5) "admin" ["spam"]=> string(1) "0" ["deleted"]=> string(1) "0" } ["ID"]=> int(1) ["caps"]=> array(1) { ["administrator"]=> bool(true) } ["cap_key"]=> string(15) "wp_capabilities" ["roles"]=> array(1) { [0]=> string(13) "administrator" } ["allcaps"]=> array(62) { ["switch_themes"]=> bool(true) ["edit_themes"]=> bool(true) ["activate_plugins"]=> bool(true) ["edit_plugins"]=> bool(true) ["edit_users"]=> bool(true) ["edit_files"]=> bool(true) ["manage_options"]=> bool(true) ["moderate_comments"]=> bool(true) ["manage_categories"]=> bool(true) ["manage_links"]=> bool(true) ["upload_files"]=> bool(true) ["import"]=> bool(true) ["unfiltered_html"]=> bool(true) ["edit_posts"]=> bool(true) ["edit_others_posts"]=> bool(true) ["edit_published_posts"]=> bool(true) ["publish_posts"]=> bool(true) ["edit_pages"]=> bool(true) ["read"]=> bool(true) ["level_10"]=> bool(true) ["level_9"]=> bool(true) ["level_8"]=> bool(true) ["level_7"]=> bool(true) ["level_6"]=> bool(true) ["level_5"]=> bool(true) ["level_4"]=> bool(true) ["level_3"]=> bool(true) ["level_2"]=> bool(true) ["level_1"]=> bool(true) ["level_0"]=> bool(true) ["edit_others_pages"]=> bool(true) ["edit_published_pages"]=> bool(true) ["publish_pages"]=> bool(true) ["delete_pages"]=> bool(true) ["delete_others_pages"]=> bool(true) ["delete_published_pages"]=> bool(true) ["delete_posts"]=> bool(true) ["delete_others_posts"]=> bool(true) ["delete_published_posts"]=> bool(true) ["delete_private_posts"]=> bool(true) ["edit_private_posts"]=> bool(true) ["read_private_posts"]=> bool(true) ["delete_private_pages"]=> bool(true) ["edit_private_pages"]=> bool(true) ["read_private_pages"]=> bool(true) ["delete_users"]=> bool(true) ["create_users"]=> bool(true) ["unfiltered_upload"]=> bool(true) ["edit_dashboard"]=> bool(true) ["update_plugins"]=> bool(true) ["delete_plugins"]=> bool(true) ["install_plugins"]=> bool(true) ["update_themes"]=> bool(true) ["install_themes"]=> bool(true) ["update_core"]=> bool(true) ["list_users"]=> bool(true) ["remove_users"]=> bool(true) ["promote_users"]=> bool(true) ["edit_theme_options"]=> bool(true) ["delete_themes"]=> bool(true) ["export"]=> bool(true) ["administrator"]=> bool(true) } ["filter"]=> NULL ["site_id":"WP_User":private]=> int(1) } }

How to deal with a such problem?