fix: codeigniter in a subdirectory + indexPage results in 404

system/HTTP/SiteURIFactory.php

@@ -111,8 +111,40 @@ public function detectRoutePath(string $protocol = ''): string
      */
     private function parseRequestURI(): string
     {
+        $appConfig = config(App::class);
+        $baseUrl   = $appConfig->baseURL;
+        $indexPage = $appConfig->indexPage;
+        $baseUri   = false;
+        $parsedUrl = parse_url($baseUrl);
+
+        if (isset($parsedUrl['path'])) { // The path could be empty if the url is just a domain
+            $baseUri = $parsedUrl['path'];
+        }
+        if ($baseUri) {
+            $baseUriArray = explode('/', $baseUri);
+            $baseUriArray = array_filter($baseUriArray); // We remove the empty strings from the array
+            $baseUri      = implode('/', $baseUriArray); // We join the array back into a string with slashes
+            if ($baseUri !== '') {
+                $baseUri = '/' . $baseUri; // We add a slash at the beginning of the base Uri as implode will not do that
+            } else {
+                $baseUri = false;
+            }
+        }
+
+        $serverRequestUri = $this->superglobals->server('REQUEST_URI'); // We get the request URI from the server superglobals
+
+        if (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 !== false && 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 (
-            $this->superglobals->server('REQUEST_URI') === null
+            $serverRequestUri === null
             || $this->superglobals->server('SCRIPT_NAME') === null
         ) {
             return '';
@@ -122,7 +154,7 @@ private function parseRequestURI(): string
         // string contains a colon followed by a number. So we attach a dummy
         // host since REQUEST_URI does not include the host. This allows us to
         // parse out the query string and path.
-        $parts = parse_url('http://dummy' . $this->superglobals->server('REQUEST_URI'));
+        $parts = parse_url('http://dummy' . $serverRequestUri);
         $query = $parts['query'] ?? '';
         $path  = $parts['path'] ?? '';