<?php
function exception_handler($exception) {
	trigger_error("user error");
	throw new Exception('exception1');
}
set_exception_handler('exception_handler');
throw new Exception('exception2');
?>

This modified code may be better illustrate the problem:

<?php
function error_handler() {
	trigger_error("inside error", E_USER_ERROR);
}
set_error_handler('error_handler');
trigger_error("outside error", E_USER_ERROR);

function exception_handler($exception) {
	throw new Exception('inside exception');
}
set_exception_handler('exception_handler');
throw new Exception('outside exception');
?>

Got the same Problem with the ErrorHandler
Just in win32. In Linux this works great.

SourceCode:
-------------------------------------------
--- header.php (Load before any output started or other PHP files loaded)
set_error_handler(array('main','handleError'), E_ALL);

--- main.class.php
final class main {
   [...]
public static function handleError($errorNo, $message, $filename, $lineNo) {
		$errReport = error_reporting();
		
		if ($errReport != 0) {
			if ($errorNo != 8) {
				$type = 'error';
				switch ($errorNo) {
					case 2: $type = 'warning';
					break;
				}
				
				throw new SystemException('PHP '.$type.' in file '.$filename.' ('.$lineNo.'): '.$message, 0);
			}
		}
	}
   [...]
}

--- systemexception.class.php (loaded before main.class.php)
require_once('exceptions/printableexception.class.php');
class SystemException extends Exception implements PrintableException {
[...]
public function show() {
echo '...[...template...]...';
}
[...]
}

--- printableexception.class.php
interface PrintableException {
public function show();
}
----------- EOF --------------

On Linux Systems: anything works great!
On Windows Systems: Exception thrown without a stack frame in Unknown on line 0

You know, "complicated" stack traces like the one you get in Java would be much more helpful than this message. Or the one in Erlang. Or in Ruby with Rails.

See also bug #43016

Does this still happen using latest CVS snapshot/checkout of PHP 5.2 branch?

No feedback was provided for this bug for over a week, so it is
being suspended automatically. If you are able to provide the
information that was originally requested, please do so and change
the status of the bug back to "Open".

Maybe related to Bug #51394

This problem is still present as of PHP 5.3.2 on Ubuntu 10.04 using the 
following test cases:

<?php
// Example 1
function exceptionHandlerFunc()
{
	throw new Exception("This message should be visible!");
}

set_exception_handler("exceptionHandlerFunc");

throw new Exception("Something bad happened");
?>
<?php
// Example 2
function shutdownFunc()
{
	throw new Exception("This message should be visible!");
}

register_shutdown_function('shutdownFunc');
?>
<?php
// Example 3
class MyClass
{
	public function __destruct()
	{
		throw new Exception("This message should be visible!");
	}
}

$test = new MyClass();
?>

All result in this error: 'Fatal error: Exception thrown without a stack frame 
in Unknown on line 0'

While I can understand their may be complexities with stack traces, and even 
file and line numbers in these contexts, the original error message should at 
least be visible so that it can be debugged and resolved, i.e. Fatal error: 
Exception (type: Exception, message: 'This message should be visible!') thrown 
without a stack frame in Unknown on line 0.

This was fixed between PHP 5.3.5 and PHP 5.3.6 in the following revision:

------------------------------------------------------------------------
r307523 | stas | 2011-01-17 08:24:43 +1100 (Mon, 17 Jan 2011) | 2 lines
Fix bug #47143, bug #51458 - provide more useful info in bad exception cases

It didn't seem to make it into the ChangeLog, though.

And it didn't reference this bug.. I guess over the past six years, there's been a 
lot of duplicate reports!