Description:
------------
When using the ++ operator on an overloaded object property that's not assigned a value, a debug_backtrace() in another unrelated object causes a crash.  See example code to reproduce the problem.

Note 1:  The script executes correctly if, in the example code...

$foo->bar++;

is replaced with...

$x = $foo->bar;
$x++;
$foo->bar = $x;

Note 2: if the __set method in class Setter actually sets the variable on the object the script executes correctly.

The bug appears in php5rc1 and the snapshot Built On: Apr 11, 2004 10:30 GMT.  crash occurs when using php as apache module or from command line.

Reproduce code:
---------------
<?php
class Setter {
   function __get($nm){ }
   function __set($nm, $val){ }
}

class Test {
	function backtrace(){
		debug_backtrace();
	}
}
$foo = new Setter();
$foo->bar++;

$t = new Test();
$t->backtrace();
?>

Expected result:
----------------
"got exception" printed

Actual result:
--------------
apache service crash