Sometimes it is not as straightforward as one may think to get the current url to use it inside your application. Here is a snippet that I use to fetch the current URL and use it in a script. The current url (whether http or https) is now a local variable that you can do with as you please.
$url = (!empty($_SERVER['HTTPS'])) ? "https://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI'] : "http://".$_SERVER['SERVER_NAME'].$_SERVER['REQUEST_URI'];
Note: You should groom this value before using in anything sensitive, like a sql query.