Before this, I've started the session, and have included the file defining the Test class.

  session_register("testCache");

  if(!isset($testCache))
  {
     $testCache = new Test($testid);
     echo "Loading non cached...";
  }

It should be noted that an instantiated Test object is really pretty darn hefty and contains arrays of objects in its attributes with many methods.  Total footprint is probably around 150k or so.

The first time this code is executed, testCache is empty
and is created within the body of the if statement

The second time (reload the page for instance) it causes the apache process servicing the request to gobble up insane amounts of memory.  As far as I can tell, apache will never respond back.  On the reload, the session variable should be set