add_action('init', 'flush_the_rewrite_rules');
add_filter('generate_rewrite_rules', 'create_rewrite_rules');
add_filter('query_vars', 'add_query_vars');
 
function create_rewrite_rules() {
	$variable='download';
	add_rewrite_rule($wordpress_root.'/'.$variable.'(/(.*))?/?$', 'index.php?pagename=$matches[1]&'.$variable.'=$matches[3]');
}
 
function flush_the_rewrite_rules () {
	flush_rewrite_rules;
}
 
function add_query_vars($public_query_vars) {
	$public_query_vars[] = 'download';
	return $public_query_vars;
}