Return types

exam/classes/Database/Database.php

@@ -8,7 +8,7 @@ class Database extends PDO
 {
   private static array $instances = [];
 
-  protected function __construct($dsn, $username = null, $password = null, array $options = null)
+  protected function __construct(string $dsn, string $username = null, string $password = null, array $options = null)
   {
     parent::__construct($dsn, $username, $password, $options);
   }