What's wrong with my function?

[ivytony]

I'm trying to customize the latest verion of pligg, I added a new table in mysql called 'stores'. I tried to get the store ID by its domain name. Here's my function in libs/html1.php:

PHP Code:

function get_category($domain){
global $db;
$sql = "SELECT * FROM " . table_stores . " WHERE domain = '$domain'";
$result = $db->get_results($sql);

    $catgoryid = $result->category_id; //category_id is a column name in the table_stores
 
  return $categoryid;
} 


Right now, this function doesn't return any value.

I've made table_stores as a constant.

Can someone help me out how to retrieve a single record from the database by using get_results?