How to hide a worpress instance behind a different apache server with mod_rewrite

I had the need to move my blog running wordpress 2.0.x to a different server, but keeping the domain name on the “old” server. I used mod_rewrite and with a lot of trial and error and some updates i finally got this working solution:

note: let’s call the origin server SERVER A and the “new” server running wordpress and mySQL SERVER B. SERVER A has only Apache 2 with mod_rewrite running, SERVER B has Apache, mySQL and PHP running.

Step 1: basic rewrite rules on SERVER A

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<IfModule mod_rewrite.c>
  RewriteEngine On
  RewriteCond %{REQUEST_METHOD} ^TRACE
  RewriteRule .* - [F]
  ##### Wordpress Rewrites
  # redirects http://<SERVER_A>/ to the blog
  RewriteRule ^/$ /blog/
  # needed for xmlrpc to work
  RewriteRule ^/blog/xmlrpc.php(.*) http://<SERVER_B>/<PATH_TO_WORDPRESS>/xmlrpc.php$1 [L,P]
  # needed for language chooser to work on pages (not posts)
  RewriteRule ^/blog/index.php/(.*)$ /blog/$1
  # rewrite everything to index.php, except pages ending with .php or directories inside wp-*
  RewriteCond %{REQUEST_URI} !^/blog/.*\.php$
  RewriteCond %{REQUEST_URI} !^/blog/wp-.*
  RewriteRule ^/blog(.*) http://<SERVER_B>/<PATH_TO_WORDPRESS>/index.php$1 [L,P]
  # special rewrites for special cases
  # contet directory rewrite
  RewriteRule ^/blog/wp-(.*)$ http://<SERVER_B>/<PATH_TO_WORDPRESS>/wp-$1 [L,P]
  # trailin slash problem
  RewriteRule ^/blog$ http://<SERVER_B>/wordpress/ [L,P]
</IfModule>

note: my blog runs on http://<SERVER A>/blog/

Step 2: configure WordPress

login to wordpress (best done before moving wordpress to SERVER B) and go to the options -> general screen in wordpress admin and set these two values:

WordPress address (URI): http://<SERVER B>/<path to wordpress>
Blog address (URI): http://<SERVER A>/blog

Step 3: hack WordPress

now comes the part that took me hours to figure out. With all the above, wordpress almost worked, but index.php always threw a 404 not found error

The problem was, that WordPress uses $_SERVER['REQUEST_URI'] to build its links and stuff, but for my setup REQUEST_URI is <path to wordpress on SERVER B>… but this isn’t right, it should be simply /blog/…

this inserted into my config.php file does the trick:

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$_SERVER['REQUEST_URI'] = str_replace('/<path to wordpress on SERVER B>/', '/blog/', $_SERVER['REQUEST_URI']);

Step 4: there’s no step 4

UPDATE for WordPress > 2.3:

wordpress 2.3 introduced some rewrite magic implemented in wp-includes/canonical.php. Unfortunately this doesn’t work with my rewrite rules, therefore i had to disable this feature:

edit <yourwordpressdirectory>/wp-includes.php and replace

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add_action('template_redirect', 'redirect_canonical');

at the end of the file with

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//add_action('template_redirect', 'redirect_canonical');

note: this has to be done each time you update your wordpress version!!!