PHP和DB2连接故障排除

I need to pull some data from a DB2 database to display on my drupal site. So far i have:

1. setup wamp
2. have php 5.3.8 running
3. have drupal running
4. and downloaded php_ibm_db2-1.9.1-5.3-nts-vc9-x86.zip
5. edited my php.ini to include extension=php_ibm_db2.dll

but when i try to run it, i get the following error in my drupal:

Fatal error: Call to undefined function db2_connect()

Is it a version issue or something else?

regards, V