Output buffer unwinding for PHP?

PHP 5 supports exception handling. When an exception occurs, PHP does stack unwinding so that it restores the state of the script... does it? No. An important state of the script does not get restored: the output. Would it not be a good idea if PHP also did some sort of output buffer unwinding? That is the idea:

<?php

exceptional_ob_start();

echo "Begin\n";
try {
    echo "Exception\n";
    throw new Exception();
} catch (Exception $e) {}
echo "End\n";

exceptional_ob_end_flush();
    
?>

And that is the only output:

Begin
End

I am not a PHP (nor webscripting) guy so I may be wrong, but I think that something like that would be very useful. It is maybe even needed for making PHP exceptions useful.