These are the minimum requirements to run Fork CMS:

• PHP 5.3.3 or higher
• The following PHP extensions should be installed and enabled:
 cURL, libxml, DOM, SimpleXML, SPL, PDO (with MySQL driver), mb_string, iconv, GD2 graphics library, json, PCRE.
• MySQL 5.0 or higher
• Apache 2.0 with .htaccess, mod_rewrite, mod_expires (optional but recommended), mod_deflate (optional) enabled.

If you're uncertain if your server matches these requirements you can execute the php_info() function.

* A howto for Lighttpd and Nginx is available.