CodeIgniter is a small and fast PHP framework. Not all of these steps are necessary to use the framework, but they result in a more secure setup where none of the framework files are ever web accessible.

1. Download the .zip
2. Create a public/ directory at the same level as the system/ directory containing asset directories: mkdir public public/images public/javascripts public/stylesheets
3. Move the index.php file into the public/ directory: mv index.php public
4. Edit the index.php file to reflect it’s new location: :%s/$system_folder = "system";/$system_folder = "..\/system";/
5. Inside of system/application/config/config.php:
   1. Set the 'base_url' to your sites URL
   2. Clear the 'index_page' config (set it to the empty string)
   3. 'enable_query_strings' if necessary
   4. Adjust the 'log_threshold'
   5. Choose a unique 'encryption_key'
   6. Turn 'sess_encrypt_cookie' on
   7. At the end of config.php add:
      

      // optionally load (and potentially override) additional config values
      if (file_exists('../system/application/config/config.local.php'))
      {
          include('config.local.php');
      }

6. Create (and promptly SVN ignore, if applicable) a config.local.php file. The file will usually only contain overrides for ‘base_url’, ‘index_page’, ‘log_threshold’, and ‘log_path’.
7. Fill out the database.php config file as necessary, potentially with a companion database.local.php file as well.
8. If you wish to remove the index.php from you URLs, create a .htaccess file like so:
   

   RewriteEngine On
   RewriteCond $1 !^(index\.php|images|stylesheets|javascripts|favicon\.ico|robots\.txt)
   RewriteRule ^(.*)$ /fresh/index.php/$1 [L]

9. Point your document root to the new public/ directory and you’re off!