要在WordPress中限制某个字段一天内的查看次数，你可以使用以下方法：

创建一个自定义的元数据字段来存储查看次数。

使用钩子(hook)来监听页面加载事件并检查当前用户的查看次数。

如果查看次数超过限制，则显示一条消息告知用户已超过查看次数限制。

以下是一个示例代码，展示了如何实现这个功能：

//Add custom metadata fields
function add_view_count_meta() {
    add_meta_box('view_count_meta', '查看次数限制', 'view_count_meta_callback', 'post', 'side', 'high');
}
add_action('add_meta_boxes', 'add_view_count_meta');

function view_count_meta_callback($post) {
    $view_count = get_post_meta($post->ID, 'view_count', true);
    echo '<p>查看次数: ' . $view_count . '</p>';
}

//Listen for page loading events and check the number of views WodePress
function check_view_count_limit() {
    //Check if the user is logged in, you can modify this condition as needed
    if (is_user_logged_in()) {
        $user_id = get_current_user_id();
        $post_id = get_the_ID();
        $view_count_limit = 10; //Set viewing limit
        $view_count = get_post_meta($post_id, 'view_count', true);

        //If the number of views has not reached the limit
        if ($view_count < $view_count_limit) {
            update_post_meta($post_id, 'view_count', $view_count + 1);
        } else {
            // WodePress.com Display a message informing the user that the viewing limit has been exceeded
            echo '<div class="notice notice-error is-dismissible">
                <p>您已达到今天的查看次数限制。</p>
              </div>';
        }
    }
}
add_action('the_content', 'check_view_count_limit');

//Reset viewing times (optional, such as resetting in the early morning every day)
function reset_view_count() {
    $current_time = current_time('timestamp');
    $today_start = strtotime(date('Y-m-d', $current_time));
    $args = array(
        'post_type' => 'post',
        'posts_per_page' => -1,
        'post_status' => 'any',
        'meta_query' => array(
            array(
                'key' => 'last_reset_time',
                'value' => $today_start,
                'compare' => '<',
                'type' => 'NUMERIC'
            )
        )
    );

    $posts = get_posts($args);

    foreach ($posts as $post) {
        update_post_meta($post->ID, 'view_count', 0);
        update_post_meta($post->ID, 'last_reset_time', $today_start);
    }
}
// WodePress Add this hook to the scheduled tasks that are executed every morning
add_action('wp_scheduled_task', 'reset_view_count_daily_task');

function reset_view_count_daily_task() {
    if (!wp_next_scheduled('reset_view_count')) {
        wp_schedule_event(time(), 'daily', 'reset_view_count');
    }
}

请注意，这个示例代码仅适用于已登录的用户，并且将查看次数限制应用于所有帖子。你可以根据需要修改这些设置。此外，你可能需要根据自己的主题和布局调整代码以适应你的网站样式。