Cannot connect with FTP server with PHP , ftp_connect()

I was trying to connect with ftp server using ftp_connect() function of PHP as shown below:

<?php

$ftp_server = "http://ftp.mozilla.org/pub/mozilla.org/";

$conn_id = ftp_connect($ftp_server) or die("Couldn't connect to $ftp_server"); 

?>

But it returns this error:

Warning: ftp_connect() [function.ftp-connect]: php_network_getaddresses: getaddrinfo failed: No such host is known. in D:\wamp\www\ftp2.php on line 6

Although this is a very common type of error, I still cannot find any solution. Can anyone provide some possible solutions?

Thank you for your time.