the following code was working to retrieve the usd price, now for some reason its not

    require 'Mysql.php';
    require 'Util.php';
    $file = file_get_contents("http://blockchain.info/ticker");
    $vars = json_decode($file, true);
    $usd = $vars['USD']['15m'];
    $net_usd = number_format((($usd) * (100 - Settings::fee)) / 100, 2);

echo $net_usd returns zero when should be the price. offering 0.1 btc to someone who can fix.