Facebook FQL返回结果PHP

If I enter the following queries in the Facebook Graph Explorer both return a result with one value:

Case 1)
SELECT user_id from like where object_id =584xxxxxxx637

{
  "data": [
    {
      "user_id": 100xxxxxxxxxxx57
    }
  ]
}

in PHP code:
$result = $facebook->api(array(
              'method' => 'fql.query',
              'query' => 'SELECT user_id from like where object_id=584xxxxxxx637'));    
var_dump($result);

returns the expected result:
array(1) { [0]=> array(1) { ["user_id"]=> string(15) "100xxxxxxxxxxx57" } }

However, for the following similar query, I also get a valid result from the graph explorer but not from PHP:

Case 2)
SELECT page_id from page_fan where uid=me() and page_id=400xxxxxxxx095
Result in Graph Explorer:

{
  "data": [
    {
      "page_id": 400xxxxxxxx095
    }
  ]
} 


in PHP
$result = $facebook->api(array(
              'method' => 'fql.query',
              'query' => 'SELECT page_id from page_fan where uid=me() and page_id=400xxxxxxxx095'));    
var_dump($result);

Output:
array(0) { }

The user is logged into Facebook for the session (hence the graph query returns a valid result)

I've no idea why!

Started off looking at this again today and suddenly it works, I have no idea why but presumably there is some caching going on somewhere. I'm happy at least that it works :)