Returning user data using facebook php sdk -

i'm trying figure out basics of facebook php sdk. i'm using pretty simple code below...

<?php  include 'facebook.php'; $app_id = "my_id"; $app_secret = "my_secret"; $facebook = new facebook(array( 'appid' => $app_id, 'secret' => $app_secret,  ));   $userid = $facebook->getuser();  echo $userid;  $userinfo = $facebook->api("/$userid");   echo $userinfo['name'];  ?> 

when ask $userid

$userid = $facebook->getuser();  echo $userid; 

i correct value. when try take next step , retrieve logged in user's name :

$userinfo = $facebook->api("/$userid");   echo $userinfo['name']; 

nothing returned. see error? thanks!

'/$userid' use literal string /$userid. want "/$userid" or '/me'