Zabbix PHP front-end, fatal error, call to undefined function

[Kalle Tuulos]

1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu
Ubuntu 16.04 LTS

2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center
zabbix-frontend-php:
  Installed: 1:2.4.7+dfsg-2ubuntu2
  Candidate: 1:2.4.7+dfsg-2ubuntu2

3) What you expected to happen
Zabbix-server-mysql and zabbix-frontend-php were installed on Ubuntu 16.04 server from standard repositories. The server already had a working Apache2, MySQL and PHP7 installation.

After installing, steps explained in here https://thedutchlab.com/blog/installing-zabbix-on-ubuntu-1404 were done in order to configure Zabbix databases and to enable php front-end. Note, as Ubuntu 16.04 comes with PHP7, I skipped the "php5-mysql" part from these installation instructions.

Earlier, I have installed Zabbix servers from Ubuntu standard repos on top of 14.04 using the same instructions. The only difference was that those servers used PHP5.

Apache modules were enabled and Apache was restarted. Zabbix server was started. I navigated to Zabbix PHP front-end page and it was expected to work normally.

4) What happened instead

After I navigated to Zabbix PHP front-end page, an empty page was displayed and following was printed to Apache2 error.log:
---8<---8<---
[Sun May 15 11:44:20.935486 2016] [:error] [pid 27479] [client xx.xx.xx.xx:50298] PHP Fatal error: Uncaught Error: Call to undefined function mb_strlen() in /usr/share/zabbix/include/classes/user/CProfile.php:330\nStack trace:\n#0 /usr/share/zabbix/include/classes/user/CProfile.php(214): CProfile::checkValueType('index.php', 3)\n#1 /usr/share/zabbix/include/menu.inc.php(351): CProfile::update('web.menu.login....', 'index.php', 3)\n#2 /usr/share/zabbix/include/page_header.php(123): zbx_construct_menu(Array, Array, Array)\n#3 /usr/share/zabbix/include/views/general.login.php(30): require_once('/usr/share/zabb...')\n#4 /usr/share/zabbix/include/classes/core/CView.php(111): include('/usr/share/zabb...')\n#5 /usr/share/zabbix/index.php(117): CView->render()\n#6 {main}\n thrown in /usr/share/zabbix/include/classes/user/CProfile.php on line 330
---8<---8<---

According to Zabbix server's logs, the server itself seemed to work normally.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: zabbix-frontend-php 1:2.4.7+dfsg-2ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
Date: Sun May 15 11:45:40 2016
InstallationDate: Installed on 2016-05-08 (6 days ago)
InstallationMedia: Ubuntu-Server 16.04 LTS "Xenial Xerus" - Release amd64 (20160420.3)
PackageArchitecture: all
SourcePackage: zabbix
UpgradeStatus: No upgrade log present (probably fresh install)

[Kalle Tuulos (kalle-tuulos)]

I'm trying to set the package to zabbix-frontend-php, but this system doesn't let me to change it.

[Logan Rosen (logan)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. This particular bug has already been reported and is a duplicate of bug 1571534, so it is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Feel free to continue to report any other bugs you may find.