Multiple TLD cookie, with db lookup

For use with Domain Access module only.

I got this idea from Multiple top level cookie domains

If you do not wish to modify 'settings.php' each time you add a top level domain (like me) with a new $cookie_domain then replace your where 'example.com' is your TLD:

$cookie_domain = 'example.com';

with this:

if (isset($_SERVER['HTTP_HOST'])) {
	// remove any sub- subsub- etc domains
	$_srv_host = explode(".", $_SERVER['HTTP_HOST']);
	$srv_host = array_reverse($_srv_host);
	$request_host = $srv_host[1] . "." . $srv_host[0]; // this gives example.com with ALL subdomains removed
	// now we check against the database
	// do not rewrite link info a second time
	preg_match("/@(.*?)\//", $db_url, $link_host);
	preg_match("/\/\/(.*?):/", $db_url, $link_user);
	preg_match("/[^mysql(i)]:(.*?)@/", $db_url, $link_pass);
	preg_match("/@(.*?)\/(.*?)$/", $db_url, $link_db);
	$link = mysql_connect($link_host[1], $link_user[1], $link_pass[1]);
	if ($link) {
		if (mysql_select_db($link_db[2], $link)) {
			/***********************************************/
			/* no - we are not using {domain} as tablename */
			/* Drupal is not yet loaded - remember?        */
			/*      do not forget to add your table prefix */
			/*      to domain => prefix_domain             */
			/***********************************************/
			$q = "SELECT subdomain, valid FROM domain WHERE subdomain LIKE '%" . $request_host . "' AND valid LIKE '1'";
			$res = mysql_query($q);
			if ($res) { // got answer
				$rows = mysql_num_rows($res);
				// yes, only one row - it's logical Mr. Spock
				if ($rows == 1) {
					$row = mysql_fetch_array($res);
					$cookie_domain = "." . $row['subdomain'];
				} else {
					// we did get 1+ rows which is no-no, use the old settings with TLD
					$cookie_domain = '.example.com';
				}
			}
		}
	} else {
		// we did not get the link, use the old settings with TLD
		$cookie_domain = '.example.com';
	}
	mysql_close($link); // behave
}

Note:
This uses database lookup - and nothing else - prior Drupal loads it's stuff.