How to get a domain and it’s TLD from a URL string using PHP and Regular Expression:
preg_match("/[a-z0-9\-]{1,63}\.[a-z\.]{2,6}$/", parse_url($_url_string, PHP_URL_HOST), $_domain_tld);
echo $_domain_tld[0];
This is particularly useful for dealing with country TLD’s, like co.uk, on.gc along with the general .com, .net, etc.
It is also capable of ruling-out multiple subdomains like: http://i83tr.cdn-2.delivery.net/homepage/sprite.png so you end up with just delivery.net.
If you are interested in sharing a regular expression that is better at handling URL strings, please post a comment below.