php json_encode kết quả mysql

$sql = mysql_query("SELECT * FROM item_details WHERE posting_id='$item_number'");
$results = array();
while($row = mysql_fetch_array($sql))
{
   $results[] = array(
      'title' => base64_decode($row['title']),
      'price' => $row['price'],
      'seller_user' => $row['user']
   );
}
$json = json_encode($results);