First time Nextcloud Installation with unknown error message

Hi,

I tried to install Nextcloud 14.0.3 on FreeBSD 11.2. I use PHP 7.2 on php-fpm with nginx.
I am able to see the info.php Website therefore php is working with on nginx.

My problem is that as soon as I unzip the file, change the owner and group to www (FreeBSD User for nginx and PHP-FPM), change the directory to 750, and the file to 640 and connect to the website via Webbrowser I am able to see the following error message in the nextcloud.log

{"reqId":"bOc5wX9ygGhjFydvRP70","level":3,"time":"2018-11-14T20:39:28+00:00","remoteAddr":"10.49.1.5","user":"--","app":"base","method":"GET","url":"\/","message":{"Exception":"ErrorException","Message":"call_user_func_array() expects parameter 1 to be a valid callback, function 'session_name' not found or invalid function name","Code":0,"Trace":[{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Session\/Internal.php","line":210,"function":"trapError","class":"OC\\Session\\Internal","type":"->","args":[0,"call_user_func_array() expects parameter 1 to be a valid callback, function 'session_name' not found or invalid function name"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Session\/Internal.php","line":53,"function":"invoke","class":"OC\\Session\\Internal","type":"->","args":["session_name",["ochwk8ttsy7c"]]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/base.php","line":424,"function":"__construct","class":"OC\\Session\\Internal","type":"->","args":["ochwk8ttsy7c"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/base.php","line":656,"function":"initSession","class":"OC","type":"::","args":[]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/base.php","line":1068,"function":"init","class":"OC","type":"::","args":[]},{"file":"\/usr\/local\/www\/nextcloud\/index.php","line":40,"args":["\/usr\/local\/www\/nextcloud\/lib\/base.php"],"function":"require_once"}],"File":"\/usr\/local\/www\/nextcloud\/lib\/private\/Session\/Internal.php","Line":183,"CustomMessage":"--"},"userAgent":"Mozilla\/5.0 (X11; Ubuntu; Linux x86_64; rv:63.0) Gecko\/20100101 Firefox\/63.0","version":""}

Unfortunately I didn’t find any similar error message during my investigation. Does anyone know the reason why nextcloud is not working at all.

BR