Authentication against existing database

[kia44]

Hello,

I am a studnet worker and I am not very familiar with PHP. The place I work for has already bought vBulletin and is looking to use vBulletin as a forum for high school teachers where they can share their ideas or whatever. We have an existing database that includes all our users and passwords and email addresses, etc. The database is set up as a web service. My job is to figure out a way (hack) to call this database as a webservice using PHP, for authentication for vBulletin and copy the authentication information in to the mysql database for the forums. In a way, we want the mysql database for the forum to be an extension of our original database. I have done some reaserach and i am not sure how to go about this. I am suppose to use a SOAP header to encrypt, authenticate and authorize users. But my main problem is just calling the database/web service with PHP. Any ideas would be appreciated.

Thanks,

Kia

P.S. I do have WSDL files and also SOAP request and response samples available to me.