var v:String = "myString";

var url:String = "http://www.yourdomain.net/script.php?val="+v;

var reqURL:URLRequest = new URLRequest(url);

var loader:URLLoader = new URLLoader(reqURL);

loader.addEventListener(Event.COMPLETE, handleComplete);

loader.dataFormat = URLLoaderDataFormat.VARIABLES;

 

function handleComplete(e:Event):void{

....

}