克服这一问题的最简单方法是创建一个自定义“getter”，从用户元中提取数据，该元将“即时”检查、清理和更新如下：

首先创建一个函数来检查用户是否存在，

function does_user_exists($user_id){
    global $wpdb;
    $user = $wpdb->get_var( $wpdb->prepare( 
        "
            SELECT user_login
            FROM $wpdb->users 
            WHERE ID = %s
        ", 
        $user_id
    ) );
    if ($user == null)
        return false;
    else
        return true;
}

function get_user_collab($user_id){
    $update_flag = false;
    $collabs = get_user_meta($user_id,\'collab_meta_key\',true);
    //loop over ids and check if the user exists, if not then we remove it
    foreach ((array)$collabs as $key => $uid) {
        if (!does_user_exists($uid)){
            unset($collabs[$key]);
            $update_flag = true;
        }
    }
    if ($update_flag)
        update_user_meta($user_id,\'collab_meta_key\',$collabs);

    return $collabs;
}