pdo doesn´t give me output

hello, my name is marko. first i had a lot of troubles with the dll´s. now i got it to work. it didn´t work because it needs zend. now it has zend dll´s and the php modules are working. therefore zend doesn´t work anymore. no idea really. but now the dll´s work with php pdo and so on. the problem i have now i get no output from my script. its an easy script only making connection and executing query. i have the feeling it stops after the connection (new pdo ....). i tried some echo´s between to see how far it comes. but after the connection it doesnt give any response. i kicked the echos out for you. <? $dbh = new PDO('oci:', 'web2', 'password'); $stmt = $dbh->prepare("SELECT U_NAME from USERID"); if ($stmt->execute()) { while ($row = $stmt->fetch()) { echo $row[0]['U_NAME']; } } ?> please tell me what to do. i´m trying now some days. thanks marko