The second message is about curl, as I suspected, it's not working. Could I add to a precompiled installation of php?

I got it!
--> I fixed the params bug: just putting: public function initialize( $name, $url/*, $na, $nb = false*/ ) {
--> I added curl support by doing:

sudo apt-get install curl libcurl3 libcurl3-dev php5-curl

sudo /etc/init.d/apache2 restart

Now the code work fine when uploading from url. I cannot still upload from file, but think I'll fix soon. Thank you a lot for your help!