Facebook fb:request-form not working - php

Question

I just tried using the example given on developers.facebook.com to open a request form and invite friends, so I changed everything accordingly but nothing happens, do I need to launch it in some way?
<?php
$api_key = '...';
$secret = '...';
require_once 'facebook.php';
// Names and links
$app_name = "...";
$app_url = "http://apps.facebook.com/.../"; // Assumes application is at http://apps.facebook.com/app-url/
$invite_href = "invite.php"; // Rename this as needed
$facebook->require_frame();
$user2 = $facebook->require_login();
if(isset($_POST["ids"])) {
echo "<center>Thank you for inviting ".sizeof($_POST["ids"])." of your friends on <b>".$app_name."</b>.<br><br>\n";
echo "<h2>Click here to return to ".$app_name.".</h2></center>";
} else {
// Retrieve array of friends who've already authorized the app.
$fql = 'SELECT uid FROM user WHERE uid IN (SELECT uid2 FROM friend WHERE uid1='.$user2.') AND is_app_user = 1';
$_friends = $facebook->api_client->fql_query($fql);
// Extract the user ID's returned in the FQL request into a new array.
$friends = array();
if (is_array($_friends) && count($_friends)) {
foreach ($_friends as $friend) {
$friends[] = $friend['uid'];
}
}
// Convert the array of friends into a comma-delimeted string.
$friends = implode(',', $friends);
// Prepare the invitation text that all invited users will receive.
$content =
"<fb:name uid=\"".$user2."\" firstnameonly=\"true\" shownetwork=\"false\"/> has started using ".$app_name." and thought it's so cool even you should try it out!\n".
"<fb:req-choice url=\"".$facebook->get_add_url()."\" label=\"Put ".$app_name." on your profile\"/>";
?>
<fb:request-form
action="<? echo $invite_href; ?>"
method="post"
type="<? echo $app_name; ?>"
content="<? echo htmlentities($content,ENT_COMPAT,'UTF-8'); ?>">
<fb:multi-friend-selector
actiontext="Here are your friends who don't have <? echo $app_name; ?> yet. Invite whoever you want -it's free!"
exclude_ids="<? echo $friends; ?>" />
</fb:request-form>
<?php
}
?>

Answer 1

hello the following code works for me
<fb:serverFbml width="760px">
<script type="text/fbml">
<fb:fbml>
<fb:request-form
action='http://apps.facebook.com/yoursite/'
method='POST'
type='photo fun'
content="Let's fun with facebook
<fb:req-choice url='http://www.yoursite.com' label='Register'/>"
<fb:multi-friend-selector actiontext="Select your friends."></fb:multi-friend-selector>
</fb:request-form>
</fb:fbml>
</script>
</fb:serverFbml>