Can't use function return value in write context

PHP Fatal error: Can't use function return value in write context in /sites/all/modules/opcache/opcache.admin.inc on line 32

It seems fixed if you use this code:

  $trimmed = trim($form_state['values']['opcache_backends']);
  if (!empty($trimmed)) {
    $backends = preg_split("/\r\n|\n|\r/", $form_state['values']['opcache_backends']);
  }