you need to include a form of some sort in your HTML with it's action attribute set as "start.php"
your method in the FORM element could be "get" or "post" and this would determine whether you'd need to retrieve the variables using one or the other.
your variable values would be set as values in "hidden"-type input elements in the form, and then you'd access the variables in your start.php script by simply referring to them as $_POST['input_element_name'] or $HTTP_POST_VARS['input_element_name'] depending on how your PHP server is running.
when you submit the form, it will reload your start.php code, but then you'll have the variables available through the method above.
if you want to securely pass some $pass var to the script, you'll need to encrypt that $pass var and store it in a database or something and call it up from there. if you place it in the form is i outlined above, anyone can view your HTML and see the password.