But of course - this is what PHP is all about. Try this in b.php:
$newresult=$_POST['$result'];
Of course, this'll only work if you pass the variable $result from file a to file b in some way, i.e. by using a form, the action of which is b.php.
If you don't have a form, you can pass the variable in a link. Page a.php contains a link to page b.php and you include the variable in the link thus:
<a href="b.php?variable=result">Go to next page</a>
The variable is now available using the GET method, i.e.
$newresult=$_GET['$result'];
HTH
Norm