Okay, I've got a few questions for you:
Why are you connecting to Oracle through ADO? Have you tried accessing it via the Oracle 9 PHP extension?
Where did you get your ADODB php library from? Have you read through its documentation to figure out how you're supposed to use it?
If you're including a library file that complains about undefined constants, then my hunch is that you should be including a different file that defines all the constants needed by the library file. Well, either that or you're supposed to define all the constants yourself. Whatever the case, the answer should be in the documentation for your ADODB library.
Also, your error message suggests that you're using the Oracle 8 call interface, but you're using oracle 9. I've never used PHP with Oracle, so I can't say for sure, but you'll probably get better results by making sure all your versions match up.