php 5.6 or php 7

mime_magic extension on. and extension fileinfo  (must be included otherwise the theme will not work)

also you need install extension=iconv.so

in last theme version (city2 plugin 1.0.3 or higher) you need only extension fileinfo and iconv

Make sure that you have the fileinfo.so or php_fileinfo.dll is enabled in the php.ini like so, that depends on your platform and version of PHP and OS:

There should be a line similar to

;extension=fileinfo.so or ;extension=php_fileinfo.dll

remove the semicolon ; (uncomment it)

extension=fileinfo.so or extension=php_fileinfo.dll

Then save and restart apache, nginx, IIS or whatever web server you are using.

If that doesn’t work, make sure that the fileinfo extension is already installed.