请教PDO为什么连接不下oracle

请问PDO为什么连接不上oracle
数据库环境Oracle 11g 64位 window server 2003
PHP环境:32位php，运行在windows XP上。
01.
02.try {

03.

04. $dbh = new PDO('oci:dbname=//172.30.1.39:1521/orcl;charset=utf8', 'scott','neusoft');

05.

06. foreach($dbh->query('SELECT * from test') as $row) {

07. print_r($row);

08. print("

---

");

09. }

10. $dbh = null;

11.} catch (PDOException $e) {

12. print "Error!: " . $e->getMessage() . "
";

13. die();

14.}

15.?>
错误：
01.Error!: SQLSTATE[HY000]: OCIEnvNlsCreate: Check the character set is valid and that PHP has access to Oracle libraries and NLS data (ext\pdo_oci\oci_driver.c:558)

如果修改成
01.
02.try {

03.

04. $dbh = new PDO('oci:dbname=//172.30.1.39:1521/orcl', 'scott','neusoft');

05.

06. foreach($dbh->query('SELECT * from test') as $row) {

07. print_r($row);

08. print("

---

");

09. }

10. $dbh = null;

11.} catch (PDOException $e) {

12. print "Error!: " . $e->getMessage() . "
";

13. die();

14.}

15.?>
则报错：
01.Error!: SQLSTATE[]: pdo_oci_handle_factory: <> (ext\pdo_oci\oci_driver.c:579)

------解决方案--------------------
检查tnsnames.ora，listener.ora中，sqlnet.ora中，日志文件看看

------解决方案--------------------
前者是字符集名称错了
关键在于后者，你的 oci 版本是否低于 oracle 版本？