Get domain with its subdomain from url

Question

I'm using this function to get domain and subdomain from a string. But If string is already my expected format, it returns null

function getDomainFromUrl($url) {
    $host = parse_url($url, PHP_URL_HOST);
    return preg_replace('/^www\./', '', $host);
}

$url = "http://abc.example.com/" -> abc.example.com | OK

$url = "http://www.example.com/" -> example.com | OK

$url = "abc.example.com" -> FAILS!

Answer 1

That is because abc.example.com is not a PHP_URL_HOST so you need to first check that it is one first. So you should do something simple like this, where if the url is doesn't have a protocol -> add it:

function addhttp($url) {
    if (!preg_match("~^(?:f|ht)tps?://~i", $url)) {
        $url = "http://" . $url;
    }
    return $url;
}

function getDomainFromUrl($url) {
    $host = parse_url($url, PHP_URL_HOST);
    if($host){
        return preg_replace('/^www\./', '', $host);
    }else{
        //not a url with protocol
        $url = addhttp($url); //add protocol
        return getDomainFromUrl($url); //run function again.
    }
}

Answer 2

Here's a pure regex solution:

function getDomainFromUrl($url) {
    if (preg_match('/^(?:https?:\/\/)?(?:(?:[^@]*@)|(?:[^:]*:[^@]*@))?(?:www\.)?([^\/:]+)/', $url, $parts)) {
        return $parts[1];
    }
    return false; // or maybe '', depending on what you need
}

getDomainFromUrl("http://abc.example.com/"); // abc.example.com

getDomainFromUrl("http://www.example.com/"); // example.com

getDomainFromUrl("abc.example.com");         // abc.example.com

getDomainFromUrl("[email protected]"); // abc.example.com

getDomainFromUrl("https://username:[email protected]"); // abc.example.com

getDomainFromUrl("https://username:[email protected]:123"); // abc.example.com

You can try it here: http://sandbox.onlinephpfunctions.com/code/3f0343bbb68b190bffff5d568470681c00b0c45c

In case you want to know more about the regex:

^                 matching must start from the beginning on the string
(?:https?:\/\/)?  an optional, non-capturing group that matches http:// and https://

(?:(?:[^@]*@)|(?:[^:]*:[^@]*@))?
                  an optional, non-capturing group that matches either *@ or *:*@ where * is any character
(?:www\.)?        an optional, non-capturing group that matches www.
([^\/:]+)          a capturing group that matches anything up until a '/', a ':', or the end of the string