How to get subdoman name from full url

Please tell me any function or reg exp to get the subdomain name from full url.

Say url is:
http://subdomain.mydomain.com

http://www.subdomain.mydomain.com

subdomain.mydomain.com


in all above URL cases i should echo subdomain

 

Say url is:
http://subdomain.mydomain.com

http://www.subdomain.mydomain.com

subdomain.mydomain.com

www is a subdomain

subdomain.mydomain
and
www.subdomain.mydomain are two different subdomains.

 

Throw this into a test.php file, I think this is what you want ?

<?php 

$domain = "http://www.this-subdomain.mydomain.com";

$regex = "#^([a-z0-9][a-z0-9\-]{1,63})\.[a-z\.]{2,63}$#i";

$domain = str_replace('http://', '', $domain);
$domain = str_replace('www.', '', $domain);

preg_match($regex, $domain, $matches);

echo "If it exist remove the http:// & www. to make the domain : ", $matches[0]," <br />"; 
echo "We then searched for the subDomain, and found : ", $matches[1]," <br />"; 

?>

PHP:

Out-Put:

If it exist remove the http:// & www. to make the domain : this-subdomain.mydomain.com
We then searched for the subDomain, and found : this-subdomain 

Code (markup):

So you echo $matches[1] for subDomain

 

subdomain.mydomain.com


subdomain.mydomain
and

 

<?php
$url = 'http://subdomain.mydomain.com';

$pattern = '(?:http://)?'; //protocol (optional)

$pattern .= '(?:www\.)?'; //www. (optional)

$pattern .= '([^\.]+)'; //subdomain

$pattern .= '\.[^\.]+\.'; //domain

$pattern .= '[^ ]+'; //tld

preg_match("~{$pattern}~i", $url, $a);

echo htmlspecialchars($a[1]);
?>

PHP:

or simplified:

<?php
$url = 'http://subdomain.mydomain.com';

$pattern = '(?:http://)?'; //protocol (optional)

$pattern .= '(?:www\.)?'; //www. (optional)

$pattern .= '([^\.]+)'; //subdomain

$pattern .= '[^ ]+'; //the rest...

preg_match("~{$pattern}~i", $url, $a);

echo htmlspecialchars($a[1]);
?>

PHP:

 

Also take alook at:

parse_url($url, PHP_URL_HOST);

PHP: