Description:
------------
error thrown on the first 'foreach' command.

server using: php 5.2.1

Reproduce code:
---------------
$query = array ('table', 'room');
$criteria = array ('table' => array ('subjects', 'teachers', 'groups', 'rooms', 'tableparts'),
	'room' => array ('rooms', 'roomtypes', 'roomcapacity', 'roomcomputercapacity', 'roomotherkeywords', 'tableparts'));
foreach ($query[] as $qry)
{
	foreach($criteria[$qry][] as $crit)
	{
		if (isset($_GET['leer_' . $qry . 'query_' . $crit. '_removekeyword']))
		{
			unset ($_SESSION['leer_' . $qry . 'query_' . $crit . '_selectedkeywords']
				[$_GET['leer_' . $qry . 'query_' . $crit. '_removekeyword']]);
		}
	}
}


Expected result:
----------------
this code should process a number of session variables. These variables have a structured name, and thus the changing parts have been put in these small arrays.

Actual result:
--------------
Fatal error: Invalid opcode 81/16/8. in /var/www/html/dokeos/main/leer/leer.php on line 198