WCF::handleException() Unhandled exception: Call to undefined function utf8_encode()

#0 /var/www/genialchat.de/wcf/lib/data/teamspeak3viewer/TeamSpeak3_Framework/Transport/TCP.php(54): TeamSpeak3_Helper_String->toUtf8()
#1 /var/www/genialchat.de/wcf/lib/data/teamspeak3viewer/TeamSpeak3_Framework/Transport/TCP.php(108): TeamSpeak3_Transport_TCP->connect()
#2 /var/www/genialchat.de/wcf/lib/data/teamspeak3viewer/TeamSpeak3_Framework/Adapter/ServerQuery.php(76): TeamSpeak3_Transport_TCP->readLine()
#3 /var/www/genialchat.de/wcf/lib/data/teamspeak3viewer/TeamSpeak3_Framework/Adapter/Abstract.php(60): TeamSpeak3_Adapter_ServerQuery->syn()
#4 /var/www/genialchat.de/wcf/lib/data/teamspeak3viewer/TeamSpeak3_Framework/TeamSpeak3.php(320): TeamSpeak3_Adapter_Abstract->__construct(Array)
#5 /var/www/genialchat.de/wcf/lib/data/teamspeak3viewer/TeamSpeak3Viewer.class.php(30): TeamSpeak3::factory(Object(TeamSpeak3_Helper_Uri))
#6 /var/www/genialchat.de/wcf/lib/system/cache/builder/TeamSpeak3ViewerCacheBuilder.class.php(32): wcf\data\teamspeak3viewer\TeamSpeak3Viewer->connect('ts.genialchat.d...', 9987, 10011, 'serveradmin', 'xQ6a35qn')
#7 /var/www/genialchat.de/wcf/lib/system/cache/builder/AbstractCacheBuilder.class.php(40): wcf\system\cache\builder\TeamSpeak3ViewerCacheBuilder->rebuild(Array)
#8 /var/www/genialchat.de/wcf/lib/page/TeamSpeak3ViewerPage.class.php(37): wcf\system\cache\builder\AbstractCacheBuilder->getData()
#9 /var/www/genialchat.de/wcf/lib/page/AbstractPage.class.php(276): wcf\page\TeamSpeak3ViewerPage->assignVariables()
#10 /var/www/genialchat.de/wcf/lib/page/AbstractPage.class.php(100): wcf\page\AbstractPage->show()
#11 /var/www/genialchat.de/wcf/lib/system/request/Request.class.php(58): wcf\page\AbstractPage->__run()
#12 /var/www/genialchat.de/wcf/lib/system/request/RequestHandler.class.php(139): wcf\system\request\Request->execute()
#13 /var/www/genialchat.de/index.php(10): wcf\system\request\RequestHandler->handle('wbb')
#14 {main}