while ($stmt->fetch()) {
       foreach($row as $key => $val)
       {
           $c[$key] = performFunction($val);
       }
       $result[] = $c;
   }

if ($stmt = $mysqli->prepare("SELECT * FROM sample WHERE t2 LIKE ?")) {
   $tt2 = '%';
     $stmt->bind_param("s", $tt2);
   $stmt->execute();

   $meta = $stmt->result_metadata();
   while ($field = $meta->fetch_field())
   {
       $params[] = &$row[$field->name];
   }

   call_user_func_array(array($stmt, 'bind_result'), $params);

   while ($stmt->fetch()) {
       foreach($row as $key => $val)
       {
           $c[$key] = $val;
       }
       $result[] = $c;
   }
     $stmt->close();
}
$mysqli->close();
print_r($result);