使用iframe应用程序中的app_data参数传输值

I have a facebook iframe application not a fan page.
When i use this code it prints well

 $signed_request = $facebook->getSignedRequest();
 print_r($signed_request);

it prints:

Array (   
[algorithm] => HMAC-SHA256   
[expires] => 1341475200   
[issued_at] => 1341470027     
[oauth_token] =>...  
[user] =>   
   Array (    
         [country] => tr   
         [locale] => en_US   
         [age] => Array ( [min] => 21 )  
         )   
         [user_id] => ...  
       )

But when i change the url in adress bar like https://apps.facebook.com/myappname/?app_data=helloand push enter it doesn't prints app_data=hello parameter in array. How can i print it?

My application is iframe app. look at this pic You can go to my app http://apps.facebook.com/gayriciddi/ and click links on homepage and see

$view = empty($_GET['view']) ? 'home' : $_GET['view'];
    echo '<br />'.$view; 
    $testid = $_REQUEST['testid'];
    echo '<br />'.$testid.'<br />';

codes are work or not

.

my index.php:

<?php
    include ('config.php');
    include ('db_fns.php');
    header('Content-type: text/html; charset=UTF-8'); 

    print_r($fbme); 

    $controller = 'page';

    $view = empty($_GET['view']) ? 'home' : $_GET['view'];
    echo '<br />'.$view; 
    $testid = $_REQUEST['testid'];
    echo '<br />'.$testid.'<br />';

    $signed_request = $facebook->getSignedRequest();
    print_r($signed_request);

    //includes home.php
    include(WEBSITE_ROOT.'/views/'.$controller.'.php');
?>

my home.php:

    <table width="601" border="0">
 <?php foreach($testler as $key => $test){?>
  <tr>
    <td width="53">&nbsp;</td>
    <td width="420"><a href="<?=FB_BASE_URL?>?view=acilis&testid=<?=$test['id']?>" target="_top"><?php echo $test['ad'];?></a></td>
    <td width="50">&nbsp;</td>
    <td width="50">&nbsp;</td>
  </tr>
 <?php } ?>
</table>

Just use $_GET['app_data'] as it's not part of the signed request like in a page tab