Send a string to php

Question

Basically this again another new research for myself.
What I'm trying to do: send out a var from as2 as a string, to a php file that would write that string down to a txt file (test.txt)
I don't know how to do it, but I have this sample on hand ( which upload a file from local computer to server).
What I'm trying to learn from this sample is how php grab data sending over from as2, so if anyone can point out which part in the php file that holds the name of the uploading object.
very grateful,
as2:
import flash.net.FileReference;
var fileRef:FileReference = new FileReference();
var oListener:Object = new Object();
fileRef.addListener(oListener);
oListener.onSelect = function(fileRef:FileReference):Void {
    tData.text = "File Name: " + fileRef.name;
tBrowse.onPress = function() {  << tBrowse is a button
    browseFiles();
function browseFiles(): Void {
    fileRef.browse();
tUpload.onPress = function() {
    uploadFile();
function uploadFile():Void {
    fileRef.upload("simplefileupload.php");
php code "simplefileupload.php"
<?php
move_uploaded_file($_FILES['Filedata']['tmp_name'], './'.$_FILES['Filedata']['name']);
?>

Answer 1

Hi, I found a online tut, I have these codes on my swf, I don't why it isn't working, do I need to import some lib?
var urlReq:URLRequest = new URLRequest ("getVars.php");
submitT.addEventListener(MouseEvent.CLICK, send2php);      <<submitT is a button
function send2php(evt:MouseEvent):void {      
    // Set the method to POST
    urlReq.method = URLRequestMethod.POST;
    // Define the variables to post   
    var urlVars:URLVariables = new URLVariables();
    urlVars.userName = 'myUsername';
    urlVars.userPass = 'myPassword';
    // Add the variables to the URLRequest
    urlReq.data = urlVars; 
    // Add the URLRequest data to a new Loader
    var loader:URLLoader = new URLLoader (urlReq);
    // Set a listener function to run when completed
    //loader.addEventListener(Event.COMPLETE, onLoginComplete);
    // Set the loader format to variables and post to the PHP
    loader.dataFormat = URLLoaderDataFormat.VARIABLES;
    loader.load(urlReq);
And these on getVars.php,
<?php
    //Grab username and password variables
    $username = $_POST['userName'];
    $password = $_POST['userPass'];
    // for additional variables use the &
    // success=true&username=$username&password=$password
    echo $username;
    echo $password;
    echo "success=true";
?>