Question

How do I send variables to the server with XMLHTTPRequest? Would I just add them to the end of the URL of the GET request, like ?variable1=?variable2=, etc?

So more or less:

XMLHttpRequest("GET", "blahblah.psp?variable1=?" + var1 + "?variable2=" + var2, true)

Answer 1

If you want to pass variables to the server using GET that would be the way yes. Remember to escape (urlencode) them properly!

It is also possible to use POST, if you dont want your variables to be visible.

A complete sample would be:

var url = "bla.php";
var params = "somevariable=somevalue&anothervariable=anothervalue";
var http = new XMLHttpRequest();

http.open("GET", url+"?"+params, true);
http.onreadystatechange = function()
{
    if(http.readyState == 4 && http.status == 200) {
        alert(http.responseText);
    }
}
http.send(null);

To test this, (using PHP) you could var_dump $_GET to see what you retrieve.