Helper function: store or retrieve traced execution data.
function batch_test_stack($data = NULL, $reset = FALSE) {
if ($reset) {
variable_del('batch_test_stack');
}
if (!isset($data)) {
return variable_get('batch_test_stack', array());
}
$stack = variable_get('batch_test_stack', array());
$stack[] = $data;
variable_set('batch_test_stack', $stack);
}