Final step doesn't work provides internal server error

Hello,

I installed Nextcloud with nginx, php-fpm and mariadb. I am able to see the modules when using info.php. I am able to see the configuration page in order to configure the Admin User, DB Connection and Data directory.

I configured all the parameter without any problems. As soon as click on the start botton the websites provides the information that an internal server error occured and I should contact the system administrator. When I look at the nextcloud.log I am able to see the following error message:

{"reqId":"oTWbT23uAOWZlIv4WkJw","level":3,"time":"2018-11-18T10:28:09+00:00","remoteAddr":"10.49.1.5","user":"--","app":"index","method":"POST","url":"\/index.php","message":{"Exception":"Error","Message":"Call to undefined function OC\\Files\\Storage\\filter_var()","Code":0,"Trace":[{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/Storage\/Common.php","line":548,"function":"scanForInvalidCharacters","class":"OC\\Files\\Storage\\Common","type":"->","args":["appdata_ochwk8ttsy7c","\\\/"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/Storage\/Common.php","line":539,"function":"verifyPosixPath","class":"OC\\Files\\Storage\\Common","type":"->","args":["appdata_ochwk8ttsy7c"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/Cache\/Scanner.php","line":134,"function":"verifyPath","class":"OC\\Files\\Storage\\Common","type":"->","args":[".","appdata_ochwk8ttsy7c"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/Cache\/Scanner.php","line":336,"function":"scanFile","class":"OC\\Files\\Cache\\Scanner","type":"->","args":["appdata_ochwk8ttsy7c",3,-1,null,false]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/Cache\/Updater.php","line":124,"function":"scan","class":"OC\\Files\\Cache\\Scanner","type":"->","args":["appdata_ochwk8ttsy7c",false,3,false]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/View.php","line":320,"function":"update","class":"OC\\Files\\Cache\\Updater","type":"->","args":["appdata_ochwk8ttsy7c",1542536889]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/View.php","line":1161,"function":"writeUpdate","class":"OC\\Files\\View","type":"->","args":[{"__class__":"OC\\Files\\Storage\\Local"},"appdata_ochwk8ttsy7c"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/View.php","line":268,"function":"basicOperation","class":"OC\\Files\\View","type":"->","args":["mkdir","\/appdata_ochwk8ttsy7c",["create","write"]]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/Node\/Folder.php","line":160,"function":"mkdir","class":"OC\\Files\\View","type":"->","args":["\/appdata_ochwk8ttsy7c"]},{"function":"newFolder","class":"OC\\Files\\Node\\Folder","type":"->","args":["appdata_ochwk8ttsy7c"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/Node\/LazyRoot.php","line":64,"function":"call_user_func_array","args":[[{"__class__":"OC\\Files\\Node\\Root"},"newFolder"],["appdata_ochwk8ttsy7c"]]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/Node\/LazyRoot.php","line":386,"function":"__call","class":"OC\\Files\\Node\\LazyRoot","type":"->","args":["newFolder",["appdata_ochwk8ttsy7c"]]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/AppData\/AppData.php","line":84,"function":"newFolder","class":"OC\\Files\\Node\\LazyRoot","type":"->","args":["appdata_ochwk8ttsy7c"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/AppData\/AppData.php","line":107,"function":"getAppDataFolder","class":"OC\\Files\\AppData\\AppData","type":"->","args":[]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/App\/AppStore\/Fetcher\/Fetcher.php","line":138,"function":"getFolder","class":"OC\\Files\\AppData\\AppData","type":"->","args":["\/"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Installer.php","line":199,"function":"get","class":"OC\\App\\AppStore\\Fetcher\\Fetcher","type":"->","args":[]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Installer.php","line":480,"function":"downloadApp","class":"OC\\Installer","type":"->","args":["bruteforcesettings"]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/private\/Setup.php","line":389,"function":"installAppBundle","class":"OC\\Installer","type":"->","args":[{"__class__":"OC\\App\\AppStore\\Bundles\\CoreBundle"}]},{"file":"\/usr\/local\/www\/nextcloud\/core\/Controller\/SetupController.php","line":67,"function":"install","class":"OC\\Setup","type":"->","args":[{"install":"true","adminlogin":"Administrator","adminpass":"aaaa","adminpass-clone":"aaaa","directory":"\/usr\/local\/www\/nextcloud\/data","dbtype":"mysql","dbuser":"nextcloud_user","dbpass":"bbbb","dbpass-clone":"bbbb","dbname":"nextcloud","dbhost":"localhost","dbIsSet":true,"directoryIsSet":true}]},{"file":"\/usr\/local\/www\/nextcloud\/lib\/base.php","line":925,"function":"run","class":"OC\\Core\\Controller\\SetupController","type":"->","args":[{"install":"true","adminlogin":"Administrator","adminpass":"aaaa","adminpass-clone":"aaaa","directory":"\/usr\/local\/www\/nextcloud\/data","dbtype":"mysql","dbuser":"nextcloud_user","dbpass":"bbbb","dbpass-clone":"bbbb","dbname":"nextcloud","dbhost":"localhost","dbIsSet":true,"directoryIsSet":true}]},{"file":"\/usr\/local\/www\/nextcloud\/index.php","line":42,"function":"handleRequest","class":"OC","type":"::","args":[]}],"File":"\/usr\/local\/www\/nextcloud\/lib\/private\/Files\/Storage\/Common.php","Line":567,"CustomMessage":"--"},"userAgent":"Mozilla\/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/67.0.3396.87 Safari\/537.36","version":"14.0.3.0"}

When I login to the nextcloud page again it shows me the same question (mysql data, admin password etc.) but as soon as I type in all data again nextcloud says that the Administrator User already existis.

Did someone had the same issue and found a solution ?
How can I force nextcloud to provide me logs incl. more information about this error ?