Fatal error: Call to undefined function: curl_init()

I encountered this message when we enabled upload from URL on Wiki4Games. To solve the problem, you just need to enable curl support in PHP. For Windows, this is done by uncommenting extension=php_curl.dll in php.ini. For Linux (at least in Ubuntu), this is done by installing php5-curl (apt-get install php-curl). Don’t forget to restart Apache (or just “apply changes” in Webmin).