Get site mapped domain echoed - WPMU DEV Domain Mapping

gistfile1.php

function tkb_get_mapped_domain($site_id = NULL){
	global $wpdb;
	
	if ($site_id === NULL){
		$site_id = get_current_blog_id();
	}
	
	$mapped_domain = $wpdb->get_var( $wpdb->prepare( "SELECT domain FROM {$wpdb->dmtable} WHERE blog_id = %d LIMIT 1", $site_id ) );
	echo $mapped_domain;
}