Show a .xml document, which contains automatically generated integers. How could i add those?

Im trying to show a specific users purchased.xml document, my problem with that is the following:

The Url does contain two generated integers. Without those two numbers i cant view their xml document.

Example purchased.xml document:

Example xml document

What im trying to do:

<?php
    $requested['username'] = '_perverted';
    $requested['integers'] = '**SHOULDBEAUTOMATICALLYADDED**'; 

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, 'hhttp://outfits.zwinky.com');
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_POSTFIELDS, '/users/'.$requested['integers'].'/'.$requested['username'].'/purchased.xml']);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($ch, CURLOPT_COOKIEFILE, $global['cookie']);
    curl_setopt($ch, CURLOPT_COOKIEJAR, $global['cookie']);
    $data = curl_exec($ch);
    curl_close($ch);       
    echo $data;
?>

So i kinda want to send the Username with a Form element to this PHP document and it should show the requested xml file.

My only problems are the integers: 220/287, which get generated for each user. Does anyone might have a idea, how i could get those numbers?

Fiddler2 shows them incase I visit a usernames profile:

For example i visit: http://ift.tt/1sgeMy8 and got fiddler open, then it would show me exactly what im searching for.

Example xml document

Does anyone have a idea?