Zabbix logout fails with 500 Internal error with PHP7

[Roman Fiedler]

Error message:

:error PHP Fatal error: Uncaught TypeError: Argument 2 passed to CFrontendApiWrapper::callMethod() must be of the type array, boolean given, called in /usr/share/zabbix/include/classes/api/wrappers/CApiWrapper.php on line 82 and defined in /usr/share/zabbix/include/classes/api/wrappers/CFrontendApiWrapper.php:61\nStack trace:\n#0 /usr/share/zabbix/include/classes/api/wrappers/CApiWrapper.php(82): CFrontendApiWrapper->callMethod('logout', false)\n#1 /usr/share/zabbix/include/classes/user/CWebUser.php(88): CApiWrapper->__call('logout', Array)\n#2 /usr/share/zabbix/index.php(49): CWebUser::logout()\n#3 {main}\n thrown in /usr/share/zabbix/include/classes/api/wrappers/CFrontendApiWrapper.php on line 61 "https://....

There are two ways to fix that issue (partially):

* Some kind of fix available to get that function running on PHP7, see https://support.zabbix.com/browse/ZBX-9700

* Zabbix does not support PHP7, but no PHP<7 package available on Xenial. As the undefined API behaviour might also trigger many hidden bugs - and some of them might have a security impact, like a broken session termination/logout definitely is - this should be at least told the user e.g. by Zabbix failing to start after update unless user sets config variable "$EnableBuggyAndRiskyPhp7UntestedModeFlag = True".

# lsb_release -rd
Description: Ubuntu 16.04.2 LTS
Release: 16.04

# apt-cache policy zabbix-frontend-php
zabbix-frontend-php:
  Installed: 1:2.4.7+dfsg-2ubuntu2.1
  Candidate: 1:2.4.7+dfsg-2ubuntu2.1
  Version table:
 *** 1:2.4.7+dfsg-2ubuntu2.1 500
        500 http://archive.ubuntu.com/ubuntu xenial-updates/universe i386 Packages
        100 /var/lib/dpkg/status
     1:2.4.7+dfsg-2ubuntu2 500
        500 http://archive.ubuntu.com/ubuntu xenial/universe i386 Packages

[Nish Aravamudan (nacc)]

I will take a look if I can find the upstream fix for this -- I have done some cursory updating to the zabbix package for PHP7 compatibility, from upstream backports.