How to share sessions between PHP and ASP.net application?

My company took some old php application over. Due to our preference to ASP.net and to the lack of any documentation from the previous developer, we do not want to spend much resources on developing in PHP. For implementing new features, we will create an Asp.net application that has the same look to the user. We want to develop a kind of 'coexisting' web application. Therefore we must share sessions between an PHP and an Asp.net webapplication project, because there is a usermanagement involved with an existing MySQL database.

(e.g. link 'A' directs to the PHP website, and link 'B' directs to the asp.net application)

How can we share the session between and PHP and an asp.net application?

And does anyone have a hint for this 'coexisting' thing, that might be useful in development?

Edit: IIS 6 would be our targeted server, altough IIS 7.5 would also be an option

I want to tell you, how I ended up doing it.

Both applications access a MySQL database and access a "session" table, which consists of a Guid, the ID of the user, and a confirmationString (I guess I encoded the IDUser in it, somehow) and a date.

Sessions are only started by the PHP application (due to the fact, that the PHP application is still the main application). A new session will result in a new entry in the log table. Every link in the PHP application, that links to the ASP.Net application contains GET-Parameters, containing the Guid etc.

The ASP.net application checks for the GET-Parameters and sets the IDUser in the ASP.Net Session, if the GET-Parameters point to an existing session.

The links pointing back to the PHP application use the same technique.

(There are also other things to consider, like timeouts or logouts, but that can be handled as well)

All in all, I'd say that my approach is useful and none of the customers complained since the deployment (over 1 year ago)

I don't think it's natively possible to share sessions between PHP and ASP.NET.

However, it might be possible by using a PHP page that reads the contents of the session, stores them in hidden fields and then call an ASP.NET page that would read these fields and load them into ASP.NET session.

Theoretically it's possible.