Not outputting top buyers?

[RuneCentre]

I've wanted to have a custom bit of PHP on my custom template for a while now, and just decided to look up the plugin feature for vBulletin. I've wrote a small bit of PHP, and set it to hook to global_start. It is activated.

Plugin objective: Load a custom PHP page I have that displays the top 10 buyers.
Plugin code:

$ch = curl_init('topbuyers.php');
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$topbuyers = curl_exec($ch);
curl_close($ch);

What I have included in my custom template:

{vb:raw topbuyers}

I'm really new to vBulletin. First time using, sorry if I'm making a basic mistake somewhere.

If necessary, here's the custom PHP file topbuyers.php: http://paste2.org/gmBKetZ9