setup_userdata( int $for_user_id = '' )

function setup_userdata($for_user_id = '') {
	global $user_login, $userdata, $user_level, $user_ID, $user_email, $user_url, $user_identity;

	if ( '' == $for_user_id )
		$for_user_id = get_current_user_id();
	$user = get_userdata( $for_user_id );

	if ( ! $user ) {
		$user_ID = 0;
		$user_level = 0;
		$userdata = null;
		$user_login = $user_email = $user_url = $user_identity = '';
		return;
	}

	$user_ID    = (int) $user->ID;
	$user_level = (int) $user->user_level;
	$userdata   = $user;
	$user_login = $user->user_login;
	$user_email = $user->user_email;
	$user_url   = $user->user_url;
	$user_identity = $user->display_name;
}