I am building a PHP application in CodeIgniter. CodeIgniter sends all requests to the main controller: index.php. However, I don't like to see index.php in the URI. For example, http://www.example.com/faq/whatever will route to http://www.example.com/index.php/faq/whatever. I need a reliable way for a script to know what it's address is, so it will know what to do with the navigation. I've used mod_rewrite, as per CodeIgniter documentation.

The rule is as follows:

RewriteEngine on
RewriteCond $1 !^(images|inc|favicon.ico|index.php|robots.txt)
RewriteRule ^(.*)$ /index.php/$1 [L] 

Normally, I would just check php_self, but in this case it's always index.php. I can get it from REQUEST_URI, PATH_INFO, etc., but I'm trying to decide which will be most reliable. Does anyone know (or know where to find) the real difference between PHP_SELF, PATH_INFO, SCRIPT_NAME, and REQUEST_URI? Thanks for your help!

Note: I've had to add spaces, as SO sees the underscore, and makes it italic for some reason.

Updated: Fixed the spaces.