DirectoryIndex index.php
RewriteEngine on
RewriteCond $1 !^(index.php|images|css|js|robots.txt|favicon.ico)
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ ./index.php/$1 [L,QSA]

$config['index_page'] = 'index.php';

$config['index_page'] = '';

Options -Indexes
Options -MultiViews

RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_URI} ^system.*
RewriteRule ^(.*)$ /index.php/$1 [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*)$ index.php/$1 [L]