Description:
------------
I encountered this problem while debugging an exception logging class.

Infinite recursion problems are a coding mistake, but I've never seen one take down Apache before. Apache will grow in size until virtual memory starts swapping. The CPU will be at 100% and eventually, appears to halt. Limits, obviously, are not being used... yet.

Reproduce code:
---------------
<?php

        class Eggception extends Exception
        {
                public function __construct($ex)
                {
                        parent::__construct($ex);
                        try {
                                // let's say that a database object throws derived Eggception
                                throw new EggceptionSubclass('It happens');

                                // this is valid (not infinitely recursive)
                                //throw new Exception('It happens');
                        } catch (Exception $e) {
                                // should swallow exception, right?
                                // not before a never-ending recursive bomb
                        }
                }
        }

        class EggceptionSubclass extends Eggception {}

        // the following causes a runaway process (memory leak &
        // CPU spike) with Apache 2.0.55 and PHP 5.1.2
        // rather quickly, all server resources become exhausted
        // without proper process limits, potentially crashing the
        // entire machine.
        throw new Eggception('Exception Bomb');
?>

Expected result:
----------------
A timeout after a large CPU spike... perhaps a stack overflow error.

An exception recursion counter that kills a script whenever it's 1,000 layers deep in an exception stack... that would be great.

Actual result:
--------------
The process (PHP or Apache, depending on which are used to execute the script) will consume as much memory allowed while pegging the CPU at 100% utilization. Kill -9 works fine.

Workarounds include ulimit and softlimit.