modifying .htaccess to remove index.php? breaks my access to the control panel

Question

I recently took over from another developer and I'm having some trouble with my .htaccess breaking my admin control panel.

My .htaccess file is as follows:

RewriteEngine On
RewriteRule ^case-studies/(.*) /articles-case-studies/$1 [L,R=301]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d

RewriteEngine On
RewriteCond %{HTTP_HOST} ^example\.com
RewriteRule (.*) http://www.example.com/$1 [R=301,L]

<FilesMatch "\.pdf$">
  header set x-robots-tag: noindex
</FilesMatch>

<IfModule mod_rewrite.c>
        RewriteEngine On
        RewriteBase /

        # Removes index.php from ExpressionEngine URLs
        RewriteCond %{THE_REQUEST} ^GET.*index\.php [NC]
        RewriteCond %{REQUEST_URI} !/system/.* [NC]
        RewriteRule (.*?)index\.php/*(.*) /$1$2 [R=301,NE,L]

        # Directs all EE web requests through the site index file
        RewriteCond %{REQUEST_FILENAME} !-f
        RewriteCond %{REQUEST_FILENAME} !-d
        RewriteRule ^(.*)$ /index.php?/$1 [L]

    RewriteCond %{REQUEST_URI} !^/php-fpm/*
</IfModule>

which does effectively remove index.php from my urls. The problem I'm having is when I try to log into the back end control panel at:

www.example.com/admin

the page just gets stuck in an infinite redirect loop. What I've noticed is that without removing index.php? when I try to login to www.example.com/admin it redirects to

www.example.com/admin/index.php?/cp/login&return=

What am I missing?

Edit:for grammar mistakes

Answer 1

EllisLab says you have to add a special rewrite condition if you rename your system folder:

If your site’s system directory (/system/) has been renamed and is still accessible by URL, modify the RewriteCond line above:

RewriteCond %{REQUEST_URI} !/newdirectoryname/.* [NC]