If you want to use PDO_OCI and get proper russian windows-1251 codepage, just add charset=CL8MSWIN1251 to your DSN.
example:
<?php
$dbc = new PDO('oci:dbname=192.168.10.145/orcl;charset=CL8MSWIN1251', 'username', 'password');
?>
Аlso setting apache/registry/system environment variable NLS_LANG to RUSSIAN_CIS.CL8MSWIN1251 may helps you.