Description:
------------
Trying to clean the buffer in a custom error handler causes script exit when that buffer has 'ob_gzhandler' as a handler. The behaviour is consistent for both PHP5 and PHP4. Note that the example works correctly if there is no callback function specified in the call to ob_start(). 

Reproduce code:
---------------
// set error handler
function errorHandler($code,$string,$filename,$line,$scope) {
    ob_end_clean();
    die('should reach here');
}
set_error_handler('errorHandler');

// use ob_gzhandler to buffer page
ob_start('ob_gzhandler');
echo 'some output';
trigger_error('encounters error',E_USER_ERROR);

Expected result:
----------------
should reach here

Actual result:
--------------
No output.