form based authentication

Hi all,

i'm looking for a possibility to use a ProxyPass secured by a form based
login page.
We have a portal with a single sign-on component which can't handle
basic authentication...
The idea is now, to secure the virtual host which contains the ProxyPass
with a php-login page which contains the username and password and
authenticates the user. The single sign-on component will do the login,
so access to the backend server is only possible via the portal.
And ideas or suggestions would be highly appreciated.

Regards,

Florian