นำ PHP เข้ามาโชว์ใน Flash as2 แล้ว return "Undefined" ???

_root.createTextField("my_txt", 1, 100, 100, 100 , 21);
my_txt.border = true;
var myLoadVars:LoadVars = new LoadVars();
myLoadVars.onLoad = function(success:Boolean) {
   if (success) { _root.my_txt.text = this.abc; 
   trace (this.abc);}
};
myLoadVars.load("testload.php");