As a little clarification: The Apache server in question is configured as a
MPM prefork.
On Wed, Aug 15, 2012 at 4:28 PM, Reto Kaiser <reto@xxxxxxxxxxxxx> wrote:
> So here's some new observations on the instance variables being NULL.
> As far as we found out this is the sequence of events:
>
> 1. Apache (MPM) received request A which executes a php script.
> 2. Within this script during the unserialization of an object an
> exception is thrown.
> 3. This exception is catched and an error message is display to
> standard output with "echo".
> 4. The script ends normally and the standard output contents are
> returned in the HTTP response.
> 5. From now on this Apache worker is "tainted", meaning that every
> subsequent request will result in:
>
> 6. The same apache worker receives request B which executes a PHP script.
> 7. Within this PHP script reading instance variables will always
> return NULL, e.g.:
>
> <?php
> class A{}
> $a = new A();
> $a->foo = 1;
> // Now: $a->foo === NULL
>
> All subsequent requests to this apache worker will behave like this.
> The constellation leading to this behavior is very hard to further
> simplify. If we throw different exceptions, or unserialize different
> objects it doesn't happen anymore...
>
>
> As a workaround we added "exit;" to the end of our php script. With a
> call to "exit" the apache worker will not get "tainted"...
>
> Regards,
> Reto
>
>
>
> On Tue, Aug 14, 2012 at 11:52 PM, Reto Kaiser <reto@xxxxxxxxxxxxx> wrote:
> > Hey,
> >
> > We have:
> > error_reporting((E_ALL | E_STRICT) & ~(E_NOTICE | E_USER_NOTICE));
> >
> > Displaying errors is disabled:
> > display_errors = Off
> >
> > We have a custom error handler which logs all errors to a file.
> > In this file we receive byeffect errors, like that the second argument
> > to "array_key_exists" should be array, but is NULL. When we further
> > debug the reason is that the second argument is an instance variable,
> > and all instance variables are NULL.
> > We're pretty sure this is a software bug, since it only happens from
> > time to time, and already happens in the first line of the php script,
> > when none of our application code was loaded.
> > For example:
> >
> > <?php
> > class A{}
> > $a = new A();
> > $a->foo = 1;
> > if ($a->foo === null) {
> > throw new Exception("strange");
> > }
> >
> > will throw an exception.
> >
> > Since it only happens from time to time, it is really hard to debug.
> > We're now trying to reproduce in a virtual machine environment, while
> > replaying the actual requests that our webserver received. When we're
> > just simulating random load on the web server it doesn't happen. So it
> > must have something to do with certain requests, and they must have
> > some strange byeffect on php, or mod_php or something related.
> >
> > Any input welcome!
> >
> > Thanks,
> > Reto
> >
> > On Tue, Aug 14, 2012 at 11:11 PM, Jim Lucas <lists@xxxxxxxxx> wrote:
> >> On 08/12/2012 05:32 AM, Reto Kaiser wrote:
> >>>
> >>> Hi,
> >>>
> >>> So I have this strange situation where I assign a classvariable a
> >>> value, but when I read the value it is NULL.
> >>>
> >>> Does anyone have an idea what could cause this, or how to further
> debug?
> >>>
> >>> Thanks,
> >>> Reto
> >>>
> >>
> >> What is your error reporting set to?
> >>
> >> Do you have display errors turned on?
> >>
> >> Are you saving your errors to a log file?
> >>
> >> --
> >> Jim Lucas
> >>
> >> http://www.cmsws.com/
> >> http://www.cmsws.com/examples/
>
