PHP获取子域但不是实际域

Question

I'm currently using the following to get the subdomain of my site

$subdomain = array_shift(explode(".",$_SERVER['HTTP_HOST'])); 

When I use this for http://www.website.com it returns "www" which is expected

However when I use this with http://website.com it returns "website" as the subdomain. How can I make absolute sure that if there is no subdomain as in that example, it returns NULL?

Thanks!

Answer 1

Please, note that in common case you should first apply parse_url to incoming data - and then use [host] key from it. As for your question, you can use something like this:

preg_match('/([^\.]+)\.[^\.]+\.[^\.]+$/', 'www.domain.com', $rgMatches);
//2-nd level check:
//preg_match('/([^\.]+)\.[^\.]+\.[^\.]+$/', 'domain.com', $rgMatches);
$sDomain = count($rgMatches)?$rgMatches[1]:null;

But I'm not sure that it's exactly what you need (since url can contain 4-th domain level e t.c.)