banned_users.php

<?php

// change these to match your app
$app_id = '1234567890';
$app_secret = 'abcdefghijklmnopqrstuvwxyz';

// init facebook class
$facebook = new Facebook( array( 'appId' => $app_id, 'secret' => $app_secret ) );

// call {app_id}/banned/ using app access_token
$banned = $facebook->api( $app_id . '/banned', array( 'access_token' => $app_id . '|' . $app_secret ) );
print_r( $banned );