$ch = curl_init();

curl_setopt($ch, CURLOPT_URL, "http://search.twitter.com/trends.json");
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

$json = curl_exec($ch);

curl_close($ch);

// $json contains the data you want
var_dump($json);