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regex – Get domain name (not subdomain) in php

Posted by: admin April 23, 2020 Leave a comment

Questions:

I have a URL which can be any of the following formats:

http://example.com
https://example.com
http://example.com/foo
http://example.com/foo/bar
www.example.com
example.com
foo.example.com
www.foo.example.com
foo.bar.example.com
http://foo.bar.example.com/foo/bar
example.net/foo/bar

Essentially, I need to be able to match any normal URL. How can I extract example.com (or .net, whatever the tld happens to be. I need this to work with any TLD.) from all of these via a single regex?

How to&Answers:

Well you can use parse_url to get the host:

$info = parse_url($url);
$host = $info['host'];

Then, you can do some fancy stuff to get only the TLD and the Host

$host_names = explode(".", $host);
$bottom_host_name = $host_names[count($host_names)-2] . "." . $host_names[count($host_names)-1];

Not very elegant, but should work.


If you want an explanation, here it goes:

First we grab everything between the scheme (http://, etc), by using parse_url‘s capabilities to… well…. parse URL’s. 🙂

Then we take the host name, and separate it into an array based on where the periods fall, so test.world.hello.myname would become:

array("test", "world", "hello", "myname");

After that, we take the number of elements in the array (4).

Then, we subtract 2 from it to get the second to last string (the hostname, or example, in your example)

Then, we subtract 1 from it to get the last string (because array keys start at 0), also known as the TLD

Then we combine those two parts with a period, and you have your base host name.

Answer:

My solution in https://gist.github.com/pocesar/5366899

and the tests are here http://codepad.viper-7.com/GAh1tP

It works with any TLD, and hideous subdomain patterns (up to 3 subdomains).

There’s a test included with many domain names.

Won’t paste the function here because of the weird indentation for code in StackOverflow (could have fenced code blocks like github)

Answer:

It is not possible to get the domain name without using a TLD list to compare with as their exist many cases with completely the same structure and length:

  1. www.db.de (Subdomain) versus bbc.co.uk (Domain)
  2. big.uk.com (SLD) versus www.uk.com (TLD)

Mozilla’s public suffix list should be the best option as it is used by all major browsers:
https://publicsuffix.org/list/public_suffix_list.dat

Feel free to use my function:

function tld_list($cache_dir=null) {
    // we use "/tmp" if $cache_dir is not set
    $cache_dir = isset($cache_dir) ? $cache_dir : sys_get_temp_dir();
    $lock_dir = $cache_dir . '/public_suffix_list_lock/';
    $list_dir = $cache_dir . '/public_suffix_list/';
    // refresh list all 30 days
    if (file_exists($list_dir) && @filemtime($list_dir) + 2592000 > time()) {
        return $list_dir;
    }
    // use exclusive lock to avoid race conditions
    if (!file_exists($lock_dir) && @mkdir($lock_dir)) {
        // read from source
        $list = @fopen('https://publicsuffix.org/list/public_suffix_list.dat', 'r');
        if ($list) {
            // the list is older than 30 days so delete everything first
            if (file_exists($list_dir)) {
                foreach (glob($list_dir . '*') as $filename) {
                    unlink($filename);
                }
                rmdir($list_dir);
            }
            // now set list directory with new timestamp
            mkdir($list_dir);
            // read line-by-line to avoid high memory usage
            while ($line = fgets($list)) {
                // skip comments and empty lines
                if ($line[0] == '/' || !$line) {
                    continue;
                }
                // remove wildcard
                if ($line[0] . $line[1] == '*.') {
                    $line = substr($line, 2);
                }
                // remove exclamation mark
                if ($line[0] == '!') {
                    $line = substr($line, 1);
                }
                // reverse TLD and remove linebreak
                $line = implode('.', array_reverse(explode('.', (trim($line)))));
                // we split the TLD list to reduce memory usage
                touch($list_dir . $line);
            }
            fclose($list);
        }
        @rmdir($lock_dir);
    }
    // repair locks (should never happen)
    if (file_exists($lock_dir) && mt_rand(0, 100) == 0 && @filemtime($lock_dir) + 86400 < time()) {
        @rmdir($lock_dir);
    }
    return $list_dir;
}
function get_domain($url=null) {
    // obtain location of public suffix list
    $tld_dir = tld_list();
    // no url = our own host
    $url = isset($url) ? $url : $_SERVER['SERVER_NAME'];
    // add missing scheme      ftp://            http:// ftps://   https://
    $url = !isset($url[5]) || ($url[3] != ':' && $url[4] != ':' && $url[5] != ':') ? 'http://' . $url : $url;
    // remove "/path/file.html", "/:80", etc.
    $url = parse_url($url, PHP_URL_HOST);
    // replace absolute domain name by relative (http://www.dns-sd.org/TrailingDotsInDomainNames.html)
    $url = trim($url, '.');
    // check if TLD exists
    $url = explode('.', $url);
    $parts = array_reverse($url);
    foreach ($parts as $key => $part) {
        $tld = implode('.', $parts);
        if (file_exists($tld_dir . $tld)) {
            return !$key ? '' : implode('.', array_slice($url, $key - 1));
        }
        // remove last part
        array_pop($parts);
    }
    return '';
}

What it makes special:

  • it accepts every input like URLs, hostnames or domains with- or without scheme
  • the list is downloaded row-by-row to avoid high memory usage
  • it creates a new file per TLD in a cache folder so get_domain() only needs to check through file_exists() if it exists so it does not need to include a huge database on every request like TLDExtract does it.
  • the list will be automatically updated every 30 days

Test:

$urls = array(
    'http://www.example.com',// example.com
    'http://subdomain.example.com',// example.com
    'http://www.example.uk.com',// example.uk.com
    'http://www.example.co.uk',// example.co.uk
    'http://www.example.com.ac',// example.com.ac
    'http://example.com.ac',// example.com.ac
    'http://www.example.accident-prevention.aero',// example.accident-prevention.aero
    'http://www.example.sub.ar',// sub.ar
    'http://www.congresodelalengua3.ar',// congresodelalengua3.ar
    'http://congresodelalengua3.ar',// congresodelalengua3.ar
    'http://www.example.pvt.k12.ma.us',// example.pvt.k12.ma.us
    'http://www.example.lib.wy.us',// example.lib.wy.us
    'com',// empty
    '.com',// empty
    'http://big.uk.com',// big.uk.com
    'uk.com',// empty
    'www.uk.com',// www.uk.com
    '.uk.com',// empty
    'stackoverflow.com',// stackoverflow.com
    '.foobarfoo',// empty
    '',// empty
    false,// empty
    ' ',// empty
    1,// empty
    'a',// empty    
);

Recent version with explanations (German):
http://www.programmierer-forum.de/domainnamen-ermitteln-t244185.htm

Answer:

$onlyHostName = implode('.', array_slice(explode('.', parse_url($link, PHP_URL_HOST)), -2));

Answer:

I recommend using TLDExtract library for all operations with domain name.

Answer:

I think the best way to handle this problem is:

$second_level_domains_regex = '/\.asn\.au$|\.com\.au$|\.net\.au$|\.id\.au$|\.org\.au$|\.edu\.au$|\.gov\.au$|\.csiro\.au$|\.act\.au$|\.nsw\.au$|\.nt\.au$|\.qld\.au$|\.sa\.au$|\.tas\.au$|\.vic\.au$|\.wa\.au$|\.co\.at$|\.or\.at$|\.priv\.at$|\.ac\.at$|\.avocat\.fr$|\.aeroport\.fr$|\.veterinaire\.fr$|\.co\.hu$|\.film\.hu$|\.lakas\.hu$|\.ingatlan\.hu$|\.sport\.hu$|\.hotel\.hu$|\.ac\.nz$|\.co\.nz$|\.geek\.nz$|\.gen\.nz$|\.kiwi\.nz$|\.maori\.nz$|\.net\.nz$|\.org\.nz$|\.school\.nz$|\.cri\.nz$|\.govt\.nz$|\.health\.nz$|\.iwi\.nz$|\.mil\.nz$|\.parliament\.nz$|\.ac\.za$|\.gov\.za$|\.law\.za$|\.mil\.za$|\.nom\.za$|\.school\.za$|\.net\.za$|\.co\.uk$|\.org\.uk$|\.me\.uk$|\.ltd\.uk$|\.plc\.uk$|\.net\.uk$|\.sch\.uk$|\.ac\.uk$|\.gov\.uk$|\.mod\.uk$|\.mil\.uk$|\.nhs\.uk$|\.police\.uk$/';
$domain = $_SERVER['HTTP_HOST'];
$domain = explode('.', $domain);
$domain = array_reverse($domain);
if (preg_match($second_level_domains_regex, $_SERVER['HTTP_HOST']) {
    $domain = "$domain[2].$domain[1].$domain[0]";
} else {
    $domain = "$domain[1].$domain[0]";
}

Answer:

There are two ways to extract subdomain from a host:

  1. The first method that is more accurate is to use a database of tlds (like public_suffix_list.dat) and match domain with it. This is a little heavy in some cases. There are some PHP classes for using it like php-domain-parser and TLDExtract.

  2. The second way is not as accurate as the first one, but is very fast and it can give the correct answer in many case, I wrote this function for it:

    function get_domaininfo($url) {
        // regex can be replaced with parse_url
        preg_match("/^(https|http|ftp):\/\/(.*?)\//", "$url/" , $matches);
        $parts = explode(".", $matches[2]);
        $tld = array_pop($parts);
        $host = array_pop($parts);
        if ( strlen($tld) == 2 && strlen($host) <= 3 ) {
            $tld = "$host.$tld";
            $host = array_pop($parts);
        }
    
        return array(
            'protocol' => $matches[1],
            'subdomain' => implode(".", $parts),
            'domain' => "$host.$tld",
            'host'=>$host,'tld'=>$tld
        );
    }
    

    Example:

    print_r(get_domaininfo('http://mysubdomain.domain.co.uk/index.php'));
    

    Returns:

    Array
    (
        [protocol] => https
        [subdomain] => mysubdomain
        [domain] => domain.co.uk
        [host] => domain
        [tld] => co.uk
    )
    

Answer:

Here’s a function I wrote to grab the domain without subdomain(s), regardless of whether the domain is using a ccTLD or a new style long TLD, etc… There is no lookup or huge array of known TLDs, and there’s no regex. It can be a lot shorter using the ternary operator and nesting, but I expanded it for readability.

// Per Wikipedia: "All ASCII ccTLD identifiers are two letters long, 
// and all two-letter top-level domains are ccTLDs."

function topDomainFromURL($url) {
  $url_parts = parse_url($url);
  $domain_parts = explode('.', $url_parts['host']);
  if (strlen(end($domain_parts)) == 2 ) { 
    // ccTLD here, get last three parts
    $top_domain_parts = array_slice($domain_parts, -3);
  } else {
    $top_domain_parts = array_slice($domain_parts, -2);
  }
  $top_domain = implode('.', $top_domain_parts);
  return $top_domain;
}

Answer:

echo getDomainOnly("http://example.com/foo/bar");

function getDomainOnly($host){
    $host = strtolower(trim($host));
    $host = ltrim(str_replace("http://","",str_replace("https://","",$host)),"www.");
    $count = substr_count($host, '.');
    if($count === 2){
        if(strlen(explode('.', $host)[1]) > 3) $host = explode('.', $host, 2)[1];
    } else if($count > 2){
        $host = getDomainOnly(explode('.', $host, 2)[1]);
    }
    $host = explode('/',$host);
    return $host[0];
}

Answer:

I had problems with the solution provided by pocesar.
When I would use for instance subdomain.domain.nl it would not return domain.nl. Instead it would return subdomain.domain.nl
Another problem was that domain.com.br would return com.br

I am not sure but i fixed these issues with the following code (i hope it will help someone, if so I am a happy man):

function get_domain($domain, $debug = false){
    $original = $domain = strtolower($domain);
    if (filter_var($domain, FILTER_VALIDATE_IP)) {
        return $domain;
    }
    $debug ? print('<strong style="color:green">&raquo;</strong> Parsing: '.$original) : false;
    $arr = array_slice(array_filter(explode('.', $domain, 4), function($value){
        return $value !== 'www';
    }), 0); //rebuild array indexes
    if (count($arr) > 2){
        $count = count($arr);
        $_sub = explode('.', $count === 4 ? $arr[3] : $arr[2]);
        $debug ? print(" (parts count: {$count})") : false;
        if (count($_sub) === 2){ // two level TLD
            $removed = array_shift($arr);
            if ($count === 4){ // got a subdomain acting as a domain
                $removed = array_shift($arr);
            }
            $debug ? print("<br>\n" . '[*] Two level TLD: <strong>' . join('.', $_sub) . '</strong> ') : false;
        }elseif (count($_sub) === 1){ // one level TLD
            $removed = array_shift($arr); //remove the subdomain
            if (strlen($arr[0]) === 2 && $count === 3){ // TLD domain must be 2 letters
                array_unshift($arr, $removed);
            }elseif(strlen($arr[0]) === 3 && $count === 3){
                array_unshift($arr, $removed);
            }else{
                // non country TLD according to IANA
                $tlds = array(
                    'aero',
                    'arpa',
                    'asia',
                    'biz',
                    'cat',
                    'com',
                    'coop',
                    'edu',
                    'gov',
                    'info',
                    'jobs',
                    'mil',
                    'mobi',
                    'museum',
                    'name',
                    'net',
                    'org',
                    'post',
                    'pro',
                    'tel',
                    'travel',
                    'xxx',
                );
                if (count($arr) > 2 && in_array($_sub[0], $tlds) !== false){ //special TLD don't have a country
                    array_shift($arr);
                }
            }
            $debug ? print("<br>\n" .'[*] One level TLD: <strong>'.join('.', $_sub).'</strong> ') : false;
        }else{ // more than 3 levels, something is wrong
            for ($i = count($_sub); $i > 1; $i--){
                $removed = array_shift($arr);
            }
            $debug ? print("<br>\n" . '[*] Three level TLD: <strong>' . join('.', $_sub) . '</strong> ') : false;
        }
    }elseif (count($arr) === 2){
        $arr0 = array_shift($arr);
        if (strpos(join('.', $arr), '.') === false && in_array($arr[0], array('localhost','test','invalid')) === false){ // not a reserved domain
            $debug ? print("<br>\n" .'Seems invalid domain: <strong>'.join('.', $arr).'</strong> re-adding: <strong>'.$arr0.'</strong> ') : false;
            // seems invalid domain, restore it
            array_unshift($arr, $arr0);
        }
    }
    $debug ? print("<br>\n".'<strong style="color:gray">&laquo;</strong> Done parsing: <span style="color:red">' . $original . '</span> as <span style="color:blue">'. join('.', $arr) ."</span><br>\n") : false;
    return join('.', $arr);
}

Answer:

Here’s one that works for all domains, including those with second level domains like “co.uk”

function strip_subdomains($url){

    # credits to gavingmiller for maintaining this list
    $second_level_domains = file_get_contents("https://raw.githubusercontent.com/gavingmiller/second-level-domains/master/SLDs.csv");

    # presume sld first ...
    $possible_sld = implode('.', array_slice(explode('.', $url), -2));

    # and then verify it
    if (strpos($second_level_domains, $possible_sld)){
        return  implode('.', array_slice(explode('.', $url), -3));
    } else {
        return  implode('.', array_slice(explode('.', $url), -2));
    }
}

Looks like there’s a duplicate question here: delete-subdomain-from-url-string-if-subdomain-is-found

Answer:

Simply try this:

   preg_match('/(www.)?([^.]+\.[^.]+)$/', $yourHost, $matches);

   echo "domain name is: {$matches[0]}\n"; 

this working for majority of domains.

Answer:

Very late, I see that you marked regex as a keyword and my function works like a charm, so far I haven’t found a url that fails:

function get_domain_regex($url){
  $pieces = parse_url($url);
  $domain = isset($pieces['host']) ? $pieces['host'] : '';
  if (preg_match('/(?P<domain>[a-z0-9][a-z0-9\-]{1,63}\.[a-z\.]{2,6})$/i', $domain, $regs)) {
    return $regs['domain'];
  }else{
    return false;
  }
}

if you want one without regex I have this one, which I am sure I also took from this post

function get_domain($url){
  $parseUrl = parse_url($url);
  $host = $parseUrl['host'];
  $host_array = explode(".", $host);
  $domain = $host_array[count($host_array)-2] . "." . $host_array[count($host_array)-1];
  return $domain;
}

They both work amazing, BUT, this took me a while to realize if the url doesn’t start with http:// or https:// it will fail so make sure the url string starts with the protocol.

Answer:

Simply try this:

<?php
  $host = $_SERVER['HTTP_HOST'];
  preg_match("/[^\.\/]+\.[^\.\/]+$/", $host, $matches);
  echo "domain name is: {$matches[0]}\n";
?>