How do I send data over the internet?

In Unity, I have a gigantic string of data, which I want to send to a web server that will accept it, parse it, and then add the appropriate data to MySQL tables.

Here is the code I have so far in Unity:

 void SendData()
 {
     WWWForm form = new WWWForm();
     form.AddField("data", _data);
     WWW w = new WWW("http://www.birnamwoodgames.com/data/test.php", form);
 }

And the page on my web site just has a form with one input, a text field called data. The form has an action, which is the php page which will write the data to the MySQL table, and it's method is POST.

But I don't get anything when I try it. Is there something I'm missing?