Determine current domain character length - php

Question

I am parsing domains and running into a problem handling subdomains. If the domain is http://www.google.co.uk, I want to obtain the length of google which is 6.
I am using parse_url() to return the host in this case www.google.co.uk like so.
$url = 'http://www.google.co.uk';
$info = parse_url($url);
// remove www. and return google.co.uk
$new = str_replace('www.','',$info['host']);
$pieces = explode(".", $new);
$len = strlen($pieces[0]); // returns character length of google = 6
echo $len;
My code doesn't work if the domain contains a subdomain like http://test.google.co.uk: it returns a length of 4; I expect it to return a length of 6.
Any ideas?

Answer 1

Output is correct. when input is http://test.google.co.uk value of parse_url('http://test.google.co.uk')['host'] is http://test.google.co.uk. When you will exploce this string on dot first element of array will be test and its length is 4.
To get google instead of test you need to replace subdomain with nothing as you did in your first example or take the second element in exploded string. E.g:
$url = 'http://test.google.co.uk';
$info = parse_url($url);
$pieces = explode(".", $info['host']);
$len = strlen($pieces[1]); // returns character length of google = 6
echo $len;

Answer 2

There is not other way than collect and hardcode all known public 2-nd level zones (like co.uk, com.ua, co.tw and so on) and filter them in your code. Be aware to detect test.example.ua as test becouse both example.com.ua and example.ua are valid domains (which is not a case with uk zone).
Your code may look like this:
function mainDomainLength($fullDomain) {
//$fullDomain = 'DOMAIN.co.uk';
$zones = array('uk' => array('co'), 'ua' => array('com', 'org'), ...);
$domainArray = explode('.', $fullDomain);
if (count($domain) > 2 && isset($zones[$domain[count($domain)-1]])) {
if (isset($zones[$domain[count($domain)-1]][$domain[count($domain)-2]])) {
return strlen($domain[count($domain)-3]);
}
} else if (count($domain) > 1) {
return strlen($domain[1]);
} else {
return strlen($domain[0]);
}
}
EDIT: By the way! Look at Get the second level domain of an URL (java). As I can understand there is the answer you need (and url to special domains collection collected be Mozilla).