I\'ve been trying to make an AJAX request to an external server. I\'ve learned so far that I need to use getJSON to do this because of security reasons ?
Now, I can\
It could be that you haven't got a callback in test.php. Also, json_encode only accepts an array:
$results = array("key" => "value");
echo $_GET['callback'] . '(' . json_encode($results) . ')';
// the callback stuff is only needed if you're requesting from different domains
jQuery automatically switches to JSONP (i.e. using script tags instead of XMLHttpRequest) when you use http://. If you have test.html and test.php on the same domain, try using relative paths (and no callbacks).