PHP

php get current domain

// Warning: This can be manipulated by hackers!
// If this is problematic, store the domain in a config file

$currentDomain = $_SERVER['SERVER_NAME'];

php get domain name from url

parse_url('http://www.website.com/hey.php', PHP_URL_HOST);

php get domain from url

$url = 'http://google.com/dhasjkdas/sadsdds/sdda/sdads.html';
$parse = parse_url($url);
echo $parse['host']; // prints 'google.com'