Send and load problems

1

im using this flash code

    achievement1=1;

var send_mc:LoadVars = new LoadVars(); 

send_mc.achievement1 = _root.achievement1; 


send_mc.sendAndLoad("http://localhost/flashtest.php", send_mc, "POST");

and i want it to do it on the same page the flash file is on which is http://localhost/flashtest.php and this is my php code


<object width="550" height="400">
      <param name="movie" value="flash.swf">
      <embed src="flash.swf" width="400" height="550"> </embed>
      <br>
      <br>
    </object>
<?php
$hi=$_POST['achievement1'];
echo $hi;
?> 
but i just get this error Notice: Undefined index: achievement1 in C:\wamp\www\flashtest.php on line 8

what am i doing wrong?