Description:
------------
PHP crashes when using user-defined exception handler to handle PDO expcetions.

Reproduce code:
---------------
function exception_handler($exception) {
	echo 'Uncaught exception: ', $exception->getMessage(), "\n";
}

set_exception_handler('exception_handler');
$dbh = new PDO('mysql:host=mysql41.localhost;port=3306;dbname=foo');


Expected result:
----------------
Uncaught exception: SQLSTATE[28000] [1045] Access denied for user 'ODBC'@'localhost2' (using password: NO)

Actual result:
--------------
Crash with this line in Apache(/2.0.58) errorlog:

[Sun May 07 03:01:26 2006] [notice] Parent: child process exited with status 3221225477 -- Restarting.