Redirect after authentication with some parameters

Hi,
I'm making my own application that will also cooperate with other application writen in PHP.
But I'm stuck at the moment. I made my own AuthenticationHandler:

Code:

---

@Override
    public void onAuthenticationSuccess(HttpServletRequest httpServletRequest,
                                        HttpServletResponse httpServletResponse,
                                        Authentication authentication) throws IOException, ServletException
    {
        AnagUser user = (AnagUser) authentication.getPrincipal();
        String username = user.getUsername();

        Collection<GrantedAuthority> grantedAuthorities = authentication.getAuthorities();

        // redirect according to granted authorities
        if (grantedAuthorities.contains(new GrantedAuthorityImpl("ROLE_ADMIN"))) {
            httpServletResponse.sendRedirect(httpServletRequest.getContextPath() + "index");
        } else if (grantedAuthorities.contains(new GrantedAuthorityImpl("ROLE_USER"))) {
            httpServletResponse.sendRedirect("www.phpapp.com");
        } else if (grantedAuthorities.contains(new GrantedAuthorityImpl("ROLE_USER_OTHER"))) {
            httpServletResponse.sendRedirect("www.phpapp.com");
        }

        super.onAuthenticationSuccess(httpServletRequest, httpServletResponse,
                authentication);
    }

---

Code is working fine but the problem is I have no idea how to sent parameters to the other php app. I don't want to use GET as it will be visible for anyone. I don't know if I can use POST or SESSION in here.
Basically in php app I want to catch those parameters and use them for authentication in other app.

It's done like this because:
- admin panel is in java app,
- user panel (specific user panel) in in php app.

Maybe I should use other approach but I don't really have access to php app.

The easiest solution I can think of would be to include a Secure Random ID in the URL that points to data in a data store that can be shared between the Java and PHP application (i.e. a database).