Having recently switched over to nginx on my server I started receiving an error stating that the function curl_init could not be loaded. Here's the command you will need to solve the problem...
SSH onto your server and run the following command to get the PHP Curl package:
sudo apt-get install php5-curl
You may need to do a server restart afterwards with the following command:
sudo service php5-fpm restart
Or if you're running apache with a similar problem:
sudo service apache2 restart