You could use POST-method in your form. That way the variables are not shown in the address line. And there is no limit in the size.
As Zmola said, you could also use sessions. This way is also good, but you still have to first send variables with POST method, and after that you can save the variables in SESSION variables. Using session varables is good if you are using many forms, because in that way you could store variables better also for later use. When using only POST, you have to send all the variables everytime you change the form(or a HTML-page).
I'd suggest that you change the 'method' from GET to POST in your forms. Then you can access the variables like this: $var=$_POST['varaible_name']