in step 1 use this code:
$catlist_ary = array(); // Result category list
while ($image_row = $site_db->fetch_array( $result )) {
$key = get_category_path( $image_row['cat_id'], 1 ).$config['category_separator'].format_text(stripslashes($org_search_keywords), 2);
$catlist_ary[$key] = (isset($catlist_ary[$key])) ? $catlist_ary[$key] + 1 : 1; // Result category list
In step 2 this:
ksort($catlist_ary); // Result category list
$catlist = "";
foreach($catlist_ary as $key => $val)
{
$catlist .= $lang['searchresult_catlist_sep'] . $key . " (".$val.")";
}