mod_rewrite rule keeps in loop - apache

Question

I am doing a quite simple rule for mod_rewrite yet I get a loop
Here are the rules:
first if I have a request like
index.php/SOMETHING.(txt,jpg,php)
I need to first check if /SOMETHING.(txt,jpg,png) exists and display it
if the file is not an index.php/SOMETING and is a real path that exists display it
if not...pass it on to the index.php/SOMETHING.(txt,jpg,php) and show index.php
It all works but the last rule if I have a unexistent txt,jpg,php
example : http://domain.com/index.php/robots1.txt
File does not exist: /Applications/XAMPP/xamppfiles/htdocs/testredir/robots1.txt
works for any other extension...
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_URI} ^index.php/.+$
RewriteRule ^index.php/(.+)\.jpg$ $1.jpg [NC,L]
RewriteRule ^index.php/(.+)\.txt$ $1.txt [NC,L]
RewriteRule ^index.php/(.+)\.php$ $1.php [NC,L]
#here I am missing a rule but if i put the following it will loop
#RewriteCond %{REQUEST_URI} -f
#RewriteRule .* index.php/$0 [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} ^index.php/.+$
RewriteRule .* index.php/$0 [PT]

Answer 1

The %{REQUEST_URI} variable always starts with a /, and you're matching against it using ^index.php/.+$, so that condition will always be false.
It looks like you want something like this:
RewriteEngine On
RewriteBase /
RewriteCond %{THE_REQUEST} \ /index\.php/(.+)\.(jpg|txt|php)
RewriteRule ^ /%1.%2 [L,R=301]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-l
RewriteRule ^(.*)$ index.php/$1 [L,PT]