Sam on "basic passing url through shortcode causing unusual problem"

here's my shortcode:

[willhill_text_link xmlurl="http://cachepricefeeds.williamhill.com/openbet_cdn?action=template&template=getHierarchyByMarketType&classId=313&marketSort=--&filterBIR=N"]

here's my function:

function willhill_text($atts) {
   extract(shortcode_atts(array(
      'xmlurl' => '',
   ), $atts));
$rss = simplexml_load_file($xmlurl);
print_r($rss);
}

add_shortcode('willhill_text_link', 'willhill_text');

If you run it, you will see an xml feed outputted. But, if you simply do this:

$rss = simplexml_load_file('http://cachepricefeeds.williamhill.com/openbet_cdn?action=template&template=getHierarchyByMarketType&classId=313&marketSort=--&filterBIR=N');
print_r($rss);

You get a different output.

It is as if the function is ignoring everything from '?action' onwards from the url being passed.

Can anybody explain why?

Thanks