fix: phpstan level=6

src/Session.php

@@ -2,9 +2,9 @@
 
 namespace ctiso;
 
-class Session 
+class Session
 {
-    function get($key)
+    function get(string $key): mixed
     {
         if (isset($_SESSION[$key])) {
             return $_SESSION[$key];
@@ -12,7 +12,7 @@ class Session
         return null;
     }
 
-    function set($key, $value)
+    function set(string|array $key, mixed $value): void
     {
         if (is_array($key)) {
             $_SESSION[strtolower(get_class($key[0]))][$key[1]] = $value;
@@ -21,17 +21,17 @@ class Session
         }
     }
 
-    function clean($key)
+    function clean(string $key): void
     {
         unset($_SESSION[$key]);
     }
 
-    function start()
+    function start(): void
     {
         @session_start();
     }
 
-    function stop()
+    function stop(): void
     {
         session_destroy();
     }