if ( ! function_exists('getDomainName'))
{
    function getDomainName($url)
    {
        $value = strtolower(trim($url));
        $url_patten = '/^(?:(?:[a-z]+):\/\/)?((?:[a-z\d\-]{2,}\.)+[a-z]{2,})(?::\d{1,5})?(?:\/[^\?]*)?(?:\?.+)?$/i';
        $domain_patten = '/([a-z\d\-]+(?:\.(?:asia|info|name|mobi|com|net|org|biz|tel|xxx|kr|co|so|me|eu|cc|or|pe|ne|re|tv|jp|tw)){1,2})(?::\d{1,5})?(?:\/[^\?]*)?(?:\?.+)?$/i';
 
        if (preg_match($url_patten, $value))
        {
            preg_match($domain_patten, $value, $matches);
            $host = (!$matches[1]) ? $value : $matches[1];
        }
        return $host;
    }
}

echo getDomainName('gnuwiz.com/index.php');