<?php
//function one - get entire domain
function fulldomain($domainb) {
    $bits = explode('/', $domainb);
    if ($bits[0]=='http:' || $bits[0]=='https:')
        {
        return $bits[0].'//'.$bits[2].'/';
        } else {
        return 'http://'.$bits[0].'/';
        }
    unset($bits);
    }
 
//function two - use regex to get entire domain
function preg_fulldomain ($domainb) {
    return 
 
preg_replace('/^((http(s)?:\/\/)?([^\/]+)(\/)?)(.*)/','$1',$domain
 
b);
    }
 
//function three - get domain and remove subdomain.
function domain($domainb)
	{
	$bits = explode('/', $domainb);
	if ($bits[0]=='http:' || $bits[0]=='https:')
		{
		$domainb= $bits[2];
		} else {
		$domainb= $bits[0];
		}
	unset($bits);
	$bits = explode('.', $domainb);
	$idz=count($bits);
	$idz-=3;
	if (strlen($bits[($idz+2)])==2) {
	$url=$bits[$idz].'.'.$bits[($idz+1)].'.'.$bits[($idz+2)];
	} else if (strlen($bits[($idz+2)])==0) {
	$url=$bits[($idz)].'.'.$bits[($idz+1)];
	} else {
	$url=$bits[($idz+1)].'.'.$bits[($idz+2)];
	}
	return $url;
	}
 
 
//below is the usage of each function
$address='http://www.subdomain.example.com/blog/index.php?id=1';
echo fulldomain($address);
echo '<br>';
echo preg_fulldomain($address);
echo '<br>';
echo domain($address);
?>