Mod-Rewrite loading files behind the DocumentRoot

Just so you know why that rule doesn't work:

The reason that it isn't able to rewrite to /home/other_files/file.html is that mod_rewrite is parsing the path as /home/webroot/home/other_files/file.html since from mod_rewrite's point of view the preceding slash is equivalent to your document root of /home/webroot.

Ryan Ahearn's suggestion is a decent one, and is likely the route you want to go.

I believe you need to add a section with

<Directory "/home/other_files">
  (options)
</Directory>

to your server configuration before apache will be able to serve anything from it. For an example, my DocumentRoot is /var/www but there is this section in the default available site:

Alias /doc/ "/usr/share/doc/"
<Directory "/usr/share/doc/">
    Options Indexes MultiViews FollowSymLinks
    AllowOverride None
    Order deny,allow
    Deny from all
    Allow from 127.0.0.0/255.0.0.0 ::1/128
</Directory>

You could then rewrite a URL to go to /doc/ and the server would know where to get the files from.

The credit goes to Ryan Aheam, but I'm going to spell it out. I'm a beginner and even with Ryan's answer I had to experiment with a few things to get the syntax right.

I wanted my DocumentRoot to be my cakephp directory. But then I had a Mantis Bug tracker that was just regular PHP and so not in the cakephp directory. The the files below I have the following working.

http://www.example.com : served by /var/www/cakephp

http://www.example.com/mantisbt : served by /var/www/html/mantisbt

File /etc/httpd/conf/httpd.conf

Alias /mantisbt/ "/var/www/html/mantisbt/"                                                                          
<Directory "/var/www/html/">                                                                                        
    AllowOverride All                                                                                               
</Directory>                                                                                                        
                                                                                                                    
<VirtualHost *:80>                                                                                                  
    ServerAdmin me@my_email.com                                                                             
    DocumentRoot /var/www/cakephp                                                                                   
    ServerName my_website.com                                                                                      
    <Directory /var/www/cakephp/>                                                                                   
        AllowOverride All                                                                                           
    </Directory>                                                                                                    
</VirtualHost>

File /var/www/cakephp/.htaccess

<IfModule mod_rewrite.c>
    RewriteEngine on
    RewriteRule    ^mantisbt/?$   /mantisbt/  [NC,L]
    RewriteRule    ^$    webroot/    [L]
    RewriteRule    (.*) webroot/$1    [L]
</IfModule>