The above api is only for image uploading (local file)

For remote upload, try:

PHP Code: 
<?php
function lulzremote($url) {
$source file_get_contents("http://lulzimg.com/upload.php?submit=lulz&url=$url");
preg_match('/\[IMG\](.*)\[\/IMG\]/'$source$match);
return 
$match[1];
}

$url 'http://ads.besthostingforums.com/ads/659.gif';
echo 
lulzremote($url);
?>