From The Smartest Wiki
SmartestExternalUrl is a class that, as its name suggests, stores a URL to a http resource outside of Smartest.
$url.host: The host name part of the URL
$url.urlencoded: An encoded version of the URL that can be safely stores as ASCII or passed via other URLs.
$url.empty: Boolean true it the SmartestExternalUrl object is empty and has not been given a value yet.
$url.stringThe value as a string.