Here's the easy way to do it via an HTTP GET request:
Now, in senduser.php, make this change in your view script:
(There are about 100 different ways I can think of to do this, but the example above is the easiest. In every case, you need to pass the "tousercommunity" value to your senduser.php script somehow, and then show it in the view when the senduser.php request loads. I used GET parameters, but you could do it via POST as well. SESSION won't work unless you pass the "tousercommunity" back to the server and it is stored in the session variables, which is usually a less-than-ideal practice for a request like this.)
The only way I can think of to make it work the way you want without tacking the "tousercommunity" parameter to the request is to store the session in the user's cookie on the first page using javascript, then pull the name from the cookie when loading senduser.php. However, this is not really the best way, and passing the parameter via GET is, in my experience, the best way to go.