в phpmyadmin запрос работает, в php нет

SELECT * FROM data,prod,categories WHERE data.prod_id = prod.prod_id 
AND data.cat_id = categories.cat_id

$adv_search_query  = "SELECT * FROM data,prod,categories WHERE data.prod_id = prod.prod_id 
                               AND data.cat_id = categories.cat_id";
$adv_search_result = mysql_query($adv_search_query);
$adv_search_data   = db_result_to_array($adv_search_result);
print_r($adv_search_data);