[WP] Block site from non-logged in users

simple-password-lockdown-wp.php

<?php
/**
 * Plugin name: Simple Password lockdown
 * Plugin URI: https://gist.github.com/1687747
 * Description: Block site from non-logged in users
 */

add_action('get_header', 'wpq_member_only_site');

function wpq_member_only_site() {

	// logged in users or visits to a specified page are allowed
	if ( !is_user_logged_in() && !is_page( 'user-registration' ) ) {

		// vars
		$redirect_after_login = 'http://' . $_SERVER["HTTP_HOST"] . $_SERVER["REQUEST_URI"];
		$login_url = wp_login_url( $redirect_after_login );

		// redirect visitors
		wp_redirect( $login_url, 302 );
		exit;

	}

}