php - actionscript does not see changes to the textbox

Here is the relevant AS3 code:

public function processLogin ():void {


        var phpVars:URLVariables = new URLVariables();

        var phpFileRequest:URLRequest = new URLRequest("php/controlpanel.php");



        phpFileRequest.method = URLRequestMethod.POST;

        phpFileRequest.data = phpVars;

        var phpLoader:URLLoader = new URLLoader();
        phpLoader.dataFormat = URLLoaderDataFormat.VARIABLES;           
        phpLoader.addEventListener(Event.COMPLETE, showResult);

        phpVars.systemCall = "checkLogin";

        phpVars.username = username.text;
        phpVars.password = password.text;

        phpLoader.load(phpFileRequest);


        if(result_text.text == "Welcome")
        {

        gotoscenetwo();

        }
        else{
        stop();
        }

        }
    public function showResult (event:Event):void {

        result_text.autoSize = TextFieldAutoSize.RIGHT;
        result_text.text = "" + event.target.data.systemResult;


        }

and my php code:

include_once "connect.php";

$username = $_POST['username'];

$password = $_POST['password'];

if ($_POST['systemCall'] == "checkLogin") {

$sql = "SELECT * FROM users WHERE username='$username' AND password='$password'";

$query = mysql_query($sql);

$login_counter = mysql_num_rows($query);

if ($login_counter > 0) {

while ($data = mysql_fetch_array($query)) {

$username = $data["username"];

print "systemResult=Welcome";

}

} else {

print "systemResult=The login details dont match our records.";

}

}

This is my mini project. My problem is if as3 finds a matching record in the MySQL database, my gotoscenetwo() function starts to work. Thank you for help.