Почему не работает скрипт просмотров php?

$page_result = mysql_query("
        SELECT 
        `pages`.`id`,
        `pages`.`page_name`, 
        `arts`.`id` AS arts_id, 
        `arts`.`title` AS arts_title, 
        `arts`.`meta_d`, 
        `arts`.`meta_k`, 
        DATE_FORMAT(`date`, '%d/%m/%y') AS date, 
        `arts`.`cat` AS arts_cat,
        `arts`.`image`, 
        `arts`.`views`, 
        `arts`.`text`, 
        `arts`.`url` AS arts_url, 
        `users`.`usr_name`,
        `users`.`id` AS usr_id,
        `category`.`id` AS cat_id,
        `category`.`cat_name`,
        `category`.`url` AS cat_url  
        FROM `pages`, `arts`, `users`, `category` 
        WHERE page_name ='art' 
        AND `arts`.`cat` = `category`.`id` 
        AND `arts`.`author` = `users`.`id` 
        AND `arts`.`url` = '$url'",$db);
        $page_value = mysql_fetch_array($page_result);
        
        $art_id = $page_value['arts_id'];
        $ip_viewer =  $_SERVER["REMOTE_ADDR"];
        
        $query_views = "
        SELECT 
        `viewer_art`.`id_art`, 
        `viewer_art`.`ip_viewer`, 
        `arts`.`id` 
        FROM `viewer_art`, `arts` 
        WHERE `viewer_art`.`id_art` = `arts`.`id` 
        AND `viewer_art`.`ip_viewer` = '$ip_viewer' 
        AND `arts`.`id` = '$art_id'";
        
        $views = mysql_query($query_views,$db);
        
        if(mysql_num_rows($views) == NULL){
            $views_insert = mysql_query("INSERT INTO `ip_viewer` (ip, id_art) VALUES ('$ip_viewer', '$id_art')",$db);
            $views_update = mysql_query("UPDATE `arts` SET `views`=`views`+1 WHERE `arts`.`url` = '$url'",$db);
          }
        
        else{
            exit;
          }