How to perform a data transfer to an external server So I'm doing a project that involves getting sensor data from several sensors, and then sending them to an external server when a tragic occurs. But I've been having trouble figuring out how to send this data, and I am welcome to advice (I'm still relatively new to Arduino coding).

I'm using an Arduino mega, with a sim900 GSM shield and an SD card. The sensors are just analog reads and a GPS.

I've looked into FTP, a Xively account and http requests to a web server but couldn't figure it out.
There is a good example of using the SubmitHttpRequest() in this article:
GPRS Shield SIM900 Arduino

You could easily modify:
mySerial.println("AT+HTTPPARA=\"URL\",\"www.yourwebsite.com/testing.php\"");

to include a string of the sensor value, and then using a PHP script to MySQL on your webserver. Maybe something like: 
http://yourwebsite.com/testing.php?sensor1=5&amp;sensor2=10