Cheers for the help people, and sorry about the late reply (busy, busy!).
In answer to your questions regarding the why's and whatnots about the situation, I have a firm background in PHP and JSP, but everyone in my present company uses VB (for application development and web development), so I can't really go writing apps that no-one understands.
The reason I find VB limiting, is the sheer lack of functions for processing strings, arrays, databases (though we do run SQL Server, if the client is willing to fork out for the rediculous hosting charges). It just takes sooooooo damned long to do in ASP what can take minutes in PHP. As well as the infuriating problems with not being able to get form or query string elements in the same script as performing a binary read. Not to mention VB's bizzarre structure, it often feels like I am programming a language developed by a small beligerant child. Etc, etc, etc.
So, to get round these problems, I often write small components (Classes) in PHP, such as Classes that upload an image and store the image path in a database along with other form data, that can be bolted on to the app, without the other developers needing to know anything about PHP accept how to instantiate an object and pass it variables etc. We are slowly migrating to ASP.NET, which looks alot more promising, so this may soon be over. But, in the mean time, I have the session problem.
The thing is, with the web developers here using DreamweaverMX, no one seems to really know exactly how ASP controls session vars. I can not find any cookies that are created by the sessions, and it doesn't appear that query strings are being passed. And I do need to be able to maintain session state while moving between PHP and ASP. There must be a way to do it. So the main question is 'Where are the ASP session vars?' and how do I grab them with PHP? I'll have a think about the points you guys have already raised, there should be a solution in here somewhere. But in the mean time, any more thoughts about the solution are greatly appreciated.
Regards.
Steve.