How to: Save image from PHP URL

Let's say I have a page, http://example.com/image.php, holding a single "flower" image, nothing else. How can I save this image from the URL with a new name (using PHP)?

$url = 'http://example.com/image.php';
$img = '/my/folder/flower.gif';
file_put_contents($img, file_get_contents($url));

Else can use cURL

$ch = curl_init('http://example.com/image.php');
$fp = fopen('/my/folder/flower.gif', 'wb');
curl_setopt($ch, CURLOPT_FILE, $fp);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_exec($ch);
curl_close($ch);
fclose($fp);