XF 1.5 Undefined index: is_admin


Well-known member
I get from time to time this error in logs. About 20 in a row.
The array of each error message is different. Like showed in this example a thread was called.
Another shows about login, another only the call of the forum itself.

I could not reproduce it. Maybe 2 weeks nothing. Than the error and than nothing again.

Any hint what can cause this? Did not change anything in the last time.

ErrorException: Undefined index: is_admin - library/XenForo/Visitor.php:417
Generiert durch: Unbekanntes Benutzerkonto, Heute um 19:51 Uhr
#0 /var/www/html/pattayaforum.net/www/forums/library/XenForo/Visitor.php(417): XenForo_Application::handlePhpError(8, 'Undefined index...', '/var/www/html/p...', 417, Array)
#1 /var/www/html/pattayaforum.net/www/forums/library/XenForo/Session.php(274): XenForo_Visitor::setup(9689, Array)
#2 /var/www/html/pattayaforum.net/www/forums/library/XenForo/Controller.php(293): XenForo_Session::startPublicSession(Object(Zend_Controller_Request_Http))
#3 /var/www/html/pattayaforum.net/www/forums/library/XenForo/Controller.php(306): XenForo_Controller->_setupSession('Index')
#4 /var/www/html/pattayaforum.net/www/forums/library/XenForo/FrontController.php(350): XenForo_Controller->preDispatch('Index', 'XenForo_Control...')
#5 /var/www/html/pattayaforum.net/www/forums/library/XenForo/FrontController.php(134): XenForo_FrontController->dispatch(Object(XenForo_RouteMatch))
#6 /var/www/html/pattayaforum.net/www/forums/index.php(13): XenForo_FrontController->run()
#7 {main}
Benötigter Status
array(3) {
["url"] => string(80) "http://www.pattayaforum.net/forums/threads/bilder-aus-angeles-city.5342/page-172"
["_GET"] => array(0) {
["_POST"] => array(0) {
I'm guessing you're using PHP 5.4 with APC? That is likely the problem; we have seen instability with APC. If possible, I'd recommend upgrading to (at least) PHP 5.6 with the built in opcache.
I'm guessing you're using PHP 5.4 with APC?


Using 5.6.14-0+deb8u1

And here my cache settings:

$config['cache'] = array(
'enabled' => true,
'frontend' => 'Core',
'frontendOptions' => array(
'caching' => true,
'automatic_serialization' => false,
'cache_id_prefix' => 'test_',
'lifetime' => 18000
'backend' => 'Xcache',
'backendOptions' => array(),
'cacheSessions' => true
The errors all happen at one time? That seems to imply something external is triggering the issue, though it could mean something triggering a different code path. Unfortunately, with it not being reproducable, that makes troubleshooting difficult. Further, looking at the code, it looks like it should almost be impossible, unless an add-on is involved, but I would expect it somewhat more often then.

Is it always this line triggering the problem?
Is it always this line triggering the problem?

No have different.


This happened all in 1 Minute.
I guess i was the one who trigger this. Even if said unknown user account.
I was not able to load the forum at the time this happen on my pc. But on my mobile it load just normal.

Access the ACP worked at this time on both. PC and mobile.
That definitely fits with the APC-style issues we've seen in the past, though I've never seen it with opcache. Just to confirm, are you seeing PHP 5.6 with opcache if you go to admin.php?tools/phpinfo ?

If so, I think we may just have to chalk this up to an oddity as I don't see how this can happen in the code (unless an add-on is involved, though I don't think that's likely to be the case).
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