Prečo mysql_fetch_array vypisuje warning?

      include "scripts/mysqlConnect.php"; // pripojenie k MySQL

      // zistovanie ci v db neexistuju rovnake udaje

      $sql = "SELECT surname, nick, mail, icq FROM users";

      $ok = mysql_query($sql);  // vykonanie poziadavky

      $right = true;

      while($row = mysql_fetch_array($ok)):

        if($row['surname'] == $surname):

          $right = false;

          $sup = "surname";

        endif;

        // este zopar podobnych if-ov

      endwhile;

      

      // zapis do db...

      if($right):

        $sql = "INSERT INTO users 

                SET name = '$name', surname = '$surname', nick = '$nick', pswd = '$pswd', mail = '$mail', icq = '$icq'";

        $ok2 = mysql_query($sql);  // vykonanie poziadavky

      endif;

      

      // presmerovanie podla spravnosti zapisu

      if ($ok2):

        $sup = "registred";

      else:

        if(!isset($sup)):

          $sup = "failed";

        endif;

      endif;

      

      // presmerovanie >> konecne

      $path = pathinfo($_SERVER['PHP_SELF']);

      header("Location: http://" . $_SERVER['SERVER_NAME'] . $path[dirname] . "/regerror.php?". $sup);