fix: limit to subdomain '*' does not work

Author: kenjis

system/Router/RouteCollection.php

@@ -1297,7 +1297,7 @@ private function getMethodParams(string $from): string
      * Compares the subdomain(s) passed in against the current subdomain
      * on this page request.
      *
-     * @param mixed $subdomains
+     * @param string|string[] $subdomains
      */
     private function checkSubdomains($subdomains): bool
     {
@@ -1330,7 +1330,7 @@ private function checkSubdomains($subdomains): bool
      * It's especially not perfect since it's possible to register a domain
      * with a period (.) as part of the domain name.
      *
-     * @return mixed
+     * @return false|string the subdomain
      */
     private function determineCurrentSubdomain()
     {
@@ -1351,7 +1351,7 @@ private function determineCurrentSubdomain()
         }
 
         // Get rid of any domains, which will be the last
-        unset($host[count($host)]);
+        unset($host[count($host) - 1]);
 
         // Account for .co.uk, .co.nz, etc. domains
         if (end($host) === 'co') {

tests/system/Router/RouteCollectionTest.php

@@ -1156,6 +1156,20 @@ public function testWithDifferentSubdomainMissing()
         $this->assertSame($expects, $routes->getRoutes());
     }
 
+    /**
+     * @see https://github.com/codeigniter4/CodeIgniter4/issues/5959
+     */
+    public function testWithNoSubdomainAndDot()
+    {
+        $_SERVER['HTTP_HOST'] = 'example.com';
+
+        $routes = $this->getCollector();
+
+        $routes->add('/objects/(:alphanum)', 'App::objectsList/$1', ['subdomain' => '*']);
+
+        $this->assertSame([], $routes->getRoutes());
+    }
+
     /**
      * @see https://github.com/codeigniter4/CodeIgniter4/issues/1692
      */