RewriteRule trigger 404 when given too many arguments - php

Question

The site I'm building at the moment is made of two main parts: The side which the general public can access, and the admin side which only authorised people can access.
It's built with basic templating such that the different sections are accessed as follow (Using RewriteRules).
Public:
http://localhost/about should be rewritten to http://localhost/index.php?page=about
Admin:
http://localhost/admin/manage-users should be rewritten to http://localhost/admin/index.php?page=manage-users
All URLs only ever have one argument. That is, public will always be localhost/PAGE and admin will always be localhost/admin/PAGE.
At the moment, I have the following .htaccess file:
RewriteEngine on
RewriteRule ^admin/([^/.]+)/?$ /admin/index.php?page=$1 [L,NC]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.*)$ index.php?page=$1 [L,NC]
This seems to work properly when you construct the URL correctly. For example, if I navigate to localhost/about or localhost/admin/manage-users both pages load correctly. But if I go to localhost/about/blah or localhost/admin/manage-users/blah, the pages load, however the CSS is non-existant. Looking at the developer tools in Chrome, it appears that this is because it's trying to load the CSS file from the directories localhost/about/css/ and localhost/admin/css/ respectively, due to the style sheet being linked to the page with a relative path. (In reality, localhost/css/ is the directory it is actually located in.)
So even though the RedirectRule ignores any extra arguments in the URL, it is trying to load relative paths with respect to the last "directory" provided in the URL.
Is there any way to completely ignore any extra ../.. arguments? Or, even better, trigger a 404 when too many arguments are provided?
UPDATE: I have just discovered that the problem is actually a lot more complex than I previously thought. As my pages only had dummy data to test out the templating files, I didn't notice it until now.
It appears than when you navigate to localhost/admin or localhost/admin/manage-users it is loading from the http://localhost/admin/index.php file, but when you navigate to localhost/admin/manage-users/blah is reverts back to loading the http://localhost/index.php file. This makes me think that there is something I need to change in the RewriteRule, though I have no idea what.

Answer 1

It is better in long term to use absolute path in your css, js, images files rather than a relative one. Which means you have to make sure path of these files start either with http:// or a slash /.
But in order to avoid making changes to your website in-mass you can use these rules to fix your css/js/images links:
RewriteEngine on
# fix CSS/js/images links
RewriteRule (?:^|/)((?:css|js|images)/.+)$ /$1 [L,R=301]
RewriteRule ^admin/([^.]+)/?$ /admin/index.php?page=$1 [L,NC,QSA]
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(.+)$ /index.php?page=$1 [L,QSA]
Don't forget to replace first rule with your actual css/js/images directories.

Answer 2

You need to either make all of your links absolute URLs (e.g. href="/css/style.css") or add a relative URL base to the header of your page:
<base href="/" />