database - PDO PHP Multiple Rows update doesn't update -

for record list script i've made form should updating 20 rows @ once, possible change whole list @ one. values retrieved $_post , should updated in database pdo. when click submit-button, nothing happends. doesn't give error, , doens't update value in database.

maybe u can help? lots of in advance.

axel

the script:

<?php     if ($_server['request_method'] == 'post')  {      $dw = $_post['dw'];     $vw = $_post['vw'];     $aw = $_post['aw'];     $titel = $_post['titel'];         $artiest = $_post['artiest'];          $a = count($dw);          $conn = new pdo('mysql:host=localhost;dbname=#dbnamr', '#dbuser', '#dbpass');          try {             $set_details = "update `top20` set `vw` = :vw, `aw` = :aw, `titel` = :titel, `artiest` = :artiest `dw` = :dw";                  $sth = $conn->prepare($set_details);              $i = 0;             while($i < $a) {                 $sth->bindparam(':dw', $dw, pdo::param_int);                         $sth->bindparam(':vw', $vw, pdo::param_int);                         $sth->bindparam(':aw', $aw, pdo::param_int);                 $sth->bindparam(':titel', $titel, pdo::param_str);                 $sth->bindparam(':artiest', $artiest, pdo::param_str);                 $sth->execute();                 $i++;             }         }         catch(pdoexception $e) {               echo "i'm sorry, there error updating database.";               echo $e->getmessage();         }         $conn = null;         } ?>