fix: fixed the codeigniter routing for installations in subdirectories with the page index 4.

I replaced the instances of ltrim with a combination of str_starts_with and substr

Author: Franky5831

system/HTTP/SiteURIFactory.php

@@ -133,9 +133,11 @@ private function parseRequestURI(): string
 
         $serverRequestUri = $this->superglobals->server('REQUEST_URI'); // We get the request URI from the server superglobals
 
-        if($baseUri && !is_null($serverRequestUri)) $serverRequestUri = ltrim($serverRequestUri, $baseUri); // We remove the base Uri from the request URI if it exists, baseUri is the path to the subdirectory
-        if($indexPage && !is_null($serverRequestUri)) $serverRequestUri = ltrim($serverRequestUri, "/" . $indexPage); // We remove the index page from the request URI if it exists
-        if(!is_null($serverRequestUri)) $serverRequestUri = "/". ltrim($serverRequestUri, '/'); // makes sure that the uri starts with a slash
+        if(!is_null($serverRequestUri)){
+            if($baseUri && str_starts_with($serverRequestUri, $baseUri)) $serverRequestUri = substr($serverRequestUri, strlen($baseUri)); // We remove the base Uri from the request URI if it exists, baseUri is the path to the subdirectory
+            if($indexPage && str_starts_with($serverRequestUri, "/" . $indexPage)) $serverRequestUri = substr($serverRequestUri, strlen("/" . $indexPage)); // We remove the index page from the request URI if it exists
+            $serverRequestUri = "/". ltrim($serverRequestUri, '/'); // makes sure that the uri starts with a slash
+        }
 
         if (
             $serverRequestUri === null