尝试使用php获取子域URL

Question

Actually I am trying to get the sub-domain URL using php. I write code below:

$sub_url = explode('.', $_SERVER['HTTP_HOST']);
$suburl = $sub_url[0];

For Example: if sub domain URL is like my.example.com the code above is giving me my which is good but if there is no sub domain then my code will return example which is not good.

I want anything before the first dot even www but if there is nothing like if URL is example.com then I want a blank value instead of example .

Answer 1

Here's a one-liner to get the subdomain:

$subdomain = join('.', explode('.', $_SERVER['HTTP_HOST'], -2))

explode with the limit parameter of -2 will split the string on each dot, ignoring the last two elements. If there are two or fewer elements, it returns an empty array.

join will assemble the resulting array back into a dot delimited string. In case you have multiple subdomains set, eg foo.bar.domain.com will return foo.bar .

If there is no subdomain, it will return an empty string.

Answer 2

I'd assume you can just check the size of the array, assuming it was always the same size, if it was any larger you may run into problems.

$sub_url = explode('.', $_SERVER['HTTP_HOST']);

if (sizeof($sub_url) > 2) {
    $suburl = $sub_url[0];
} else {
    $suburl = null;
}

Answer 3

You should notice that, there are also websites with second level domains, for example co.uk , com.cn . If you can make sure, that your code will not be used on such website, you can simple use the answer of DarthJDG or check count($sub_url) > 2 . But if not, you need to check the domain name.

$secondLevelDomainsList = str_getcsv(file_get_contents('https://raw.github.com/gavingmiller/second-level-domains/master/SLDs.csv'), PHP_EOL);
foreach($secondLevelDomainsList as &$item) {
    list($tld, $stld) = str_getcsv($item, ",");
    $item = $stld;
}    
$urlParts = explode('.', $url);    
$challenger = '.' . join('.', array_slice($urlParts, -2, 2, true));    
$length = in_array($challenger, $secondLevelDomainsList) ? -3 : -2;    
$subDomainName = join('.', array_slice($urlParts, 0, $length, true));

The list of second level domains in format of CSV from gavingmiller/second-level-domains github repository is used for the test, if the domain is a second level domain.