请教php，pdo如何连接oracle数据库

php.ini

;extension=php_bz2.dll
extension=php_curl.dll
;extension=php_dba.dll
;extension=php_dbase.dll
extension=php_exif.dll
;extension=php_fdf.dll
extension=php_gd2.dll
;extension=php_gettext.dll
;extension=php_gmp.dll
;extension=php_ifx.dll
;extension=php_imap.dll
;extension=php_interbase.dll
;extension=php_ldap.dll
extension=php_mbstring.dll
;extension=php_mcrypt.dll
;extension=php_mhash.dll
;extension=php_mime_magic.dll
;extension=php_ming.dll
;extension=php_msql.dll
;extension=php_mssql.dll
extension=php_mysql.dll
extension=php_mysqli.dll
extension=php_oci8.dll
;extension=php_openssl.dll
extension=php_pdo.dll
extension=php_pdo_firebird.dll
extension=php_pdo_mssql.dll
extension=php_pdo_mysql.dll
extension=php_pdo_oci.dll
extension=php_pdo_oci8.dll
extension=php_pdo_odbc.dll
extension=php_pdo_pgsql.dll
extension=php_pdo_sqlite.dll
;extension=php_pgsql.dll
;extension=php_pspell.dll
;extension=php_shmop.dll
;extension=php_snmp.dll
;extension=php_soap.dll
extension=php_sockets.dll
extension=php_sqlite.dll
;extension=php_sybase_ct.dll
;extension=php_tidy.dll
;extension=php_xmlrpc.dll
;extension=php_xsl.dll
;extension=php_zip.dll

php代码
new PDO("oci:dbname=//192.168.175.40:1521/ORCL,demo,demo");
phpinfo

错误
pdo_oci_handle_factory: ORA-12514: TNS: 监听程序当前无法识别连接描述符中请求的服务 (extpdo_ocioci_driver.c:581)222