Dynamic url in facebook app tab

I am newbie to facebook app and I am trying to create a first app of my php application as an iframe, I have created the app using

http://developer.facebook.com.

but in page tab url, I need some dynamic url like: I want to set url like :

http://mydomain.com/index.php?r=site/index&user_id=some_dynamic_value

How can I set this dynamic url for a tab url, can any one suggest me please

Solution

if you want to display different content on page tab depending on pages that using this apps.Here is my code of a simple app...

    <?php
    include_once 'facebook.php';
    include_once 'class/database.class.php';
    $db = new Database();
    $app_id = "$your_app_id";
    $app_secret = "$your_app_secret_key";
    $facebook = new Facebook(array(
    'appId' => $app_id,
    'secret' => $app_secret,
    'cookie' => true
    ));
    ?>
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <head>
      <!-- Header content -->
    </head>
    <body>
    <!-- Your body Content Here -->   
    <div>
    <div>
    <?php
    $signed_request = $facebook->getSignedRequest();

    $page_id = $signed_request["page"]["id"];
    $app_id = $signed_request["page"]["id"];
    $page_admin = $signed_request["page"]["admin"];
    $like_status = $signed_request["page"]["liked"];
    $country = $signed_request["user"]["country"];
    $locale = $signed_request["user"]["locale"];

    if($page_id){
        $sql="select * from coupon where page_id=" . $page_id . "";
        $result=$db->fetch_all_array($sql);
        $heading=$result[0]['heading'];
        $desc=$result[0]['desc'];
        $img=$result[0]['img']; 
    ?>
    <h1><?php echo $heading?></h1>
    <img src="<?php echo $img; ?>">
    <p><?php echo $desc; 
    }
    ?></p>
    </div>
    </div> 
    </body>
    </html>