Twitch CustomAPI - Uptime

<?php
// Set names to lowercase for URL injection.
$BroadcasterLower = strtolower($_GET["Broadcaster"]);
// Set timezone to match Twitch servers for JSON date/ time.
date_default_timezone_set("Greenwich");
// Inject lowercase name.
$ch = curl_init("https://api.twitch.tv/kraken/streams/" . $BroadcasterLower);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result = curl_exec($ch);
curl_close($ch);
// Decode the above JSON data.
$StreamData = json_decode($result, true);
$UpTimeDateTime =date('Y-m-d H:i:s', strtotime($StreamData['stream']['created_at']));

// Stream offline
if($StreamData['stream'] == null)
{
    echo 'Sorry, ' . htmlspecialchars($_GET["Broadcaster"]) . ' isn\'t currently streaming, check back later or follow and enable notifications to know when ' . htmlspecialchars($_GET["Broadcaster"]) . ' streams next!';
    die();
}

echo $StreamData['stream']['channel']['display_name'] . ' has been streaming ' . $StreamData['stream']['channel']['game'] . ' for the past ';
echo GetDateDifference($UpTimeDateTime);
echo '.';

// Function to get the date difference.
function GetDateDifference($datetime)
{
    $now = new DateTime;
    $ago = new DateTime($datetime);
    $diff = $now->diff($ago);

    $diff->w = floor($diff->d / 7);
    $diff->d -= $diff->w * 7;

    $string = array
    (
        'y' => 'year',
        'm' => 'month',
        'w' => 'week',
        'd' => 'day',
        'h' => 'hour',
        'i' => 'minute',
        's' => 'second',
    );
    foreach ($string as $k => &$v) {
        if ($diff->$k) {
            $v = $diff->$k . ' ' . $v . ($diff->$k > 1 ? 's' : '');
        }
        else
        {
            unset($string[$k]);
        }
    }
    return $string ? implode(', ', $string) . '' : '';
}
?>

Example: Uptime.php?Broadcaster=TwitchBroadcaster