Disable a PHP website temporarily - php

Question

I have a PHP website that I own. I want to temporarily disable the website while I am making my changes (there are a lot to do). I tried to rename the index.php file but the end-user can always navigate to a page by typing the URL ( or if he had bookmarked the page ). Is there a way I can disable the whole website temporarily?
Edit : This accepted answers work for an apache web server. What I am using presently is IIS6 ( and not IIS7 where the same rewrite can be done in web.config file ). Is there a way around for this problem in IIS6?

Answer 1

You can use .htaccess file to redirect to maintenance page:
RewriteEngine On
RewriteBase /
RewriteCond %{REMOTE_ADDR} !^123\.456\.789\.000
RewriteCond %{REQUEST_URI} !^/maintenance\.html$
RewriteRule ^(.*)$ http://domain.com/maintenance.html [R=307,L]
Some useful links:
http://www.shellhacks.com/en/Redirect-Site-to-Maintenance-Page-using-Apache-and-HTAccess
http://perishablepress.com/htaccess-redirect-maintenance-page-site-updates/
http://wp-mix.com/maintenance-mode-htaccess/

Answer 2

While bartek beat me to an Apache mod_rewrite rule that would force the site to redirect all traffic to a maintenance/offline page, I wanted to post my variation on the idea which can allow a specific IP address to access the site:
RewriteEngine On
RewriteCond %{REMOTE_ADDR} !^123.45.67.890$
RewriteCond %{REMOTE_ADDR} !^127.0.0.1$
RewriteCond %{REMOTE_ADDR} !^::1$
RewriteCond %{REQUEST_URI} !^/offline.html$
RewriteRule ^(.*)$ http://your.great.website/offline.html [R=302,L]
Just a note that depending on your version of Apache, you might have to escape the . and : in the IP addresses like this:
RewriteCond %{REMOTE_ADDR} !^123\.45\.67\.890$
RewriteCond %{REMOTE_ADDR} !^127\.0\.0\.1$
RewriteCond %{REMOTE_ADDR} !^\:\:1$
The idea is if the visitor is not coming from the IP address 123.45.67.890—or the localhost addresses of 127.0.0.1 (IPv4) or ::1 (IPv6)—and the URI requested is not /offline.html then redirect that person to http://your.great.website/offline.html.
Which means you should just replace 123.45.67.890 with the IP address you would be connecting from to allow you to have a window into the website while you perform work. But anyone else who is not 123.45.67.890? Well, they see the offline.html page.

Answer 3

I would also propose this solution.
RewriteEngine On
RewriteCond %{QUERY_STRING} !access=dbcaf771cc0c4e23a0fc895d0afa106f
RewriteCond %{REQUEST_URI} !^/maintenance.html$
RewriteRule ^(.*)$ /maintenance.html [R=302,L]
The idea is unless your request contains access=dbcaf771cc0c4e23a0fc895d0afa106f within the query string, you'll simply get redirected to the maintenance page.