Further syntax errors

src/Hash/HMAC_SHA1.php

@@ -20,7 +20,7 @@ class HMAC_SHA1 implements HashInterface
         return $this->hash($key, \dechex($val));
     }
 
-    public function hashType(): string
+    public static function hashType(): string
     {
         return "SHA1";
     }
@@ -28,7 +28,7 @@ class HMAC_SHA1 implements HashInterface
     /** @SuppressWarnings(PHPMD.StaticAccess) */
     public static function keygen(): string
     {
-        return Base32::encodeUpper(random_bytes(this.DEFAULT_SECRET_SIZE));
+        return Base32::encodeUpper(random_bytes(this::DEFAULT_SECRET_SIZE));
     }
 }
 

src/HashInterface.php

@@ -6,7 +6,7 @@ interface HashInterface
 {
     public function hash(string $key, string $val): string;
     public function hashNumeric(string $key, int $val): string;
-    public function hashType(): string;
+    public static function hashType(): string;
     public static function keygen(): string;
 }
 

src/Required/PersistenceInterface.php

@@ -47,7 +47,7 @@ interface PersistenceInterface
      * @param mixed $index Whatever data needed to index into your database and identify a particular user
      * @return null|string
      */
-    public function getSecret(mixed $index): null|string;
+    public function getSecret(mixed $index): ?string;
 
     /**
      * Gets and returns the last successful challenge timestamp to enforce the One-Time aspect of a TOTP.

src/Session/Base.php

@@ -40,7 +40,12 @@ class Base implements SessionInterface
 
     public function get(string $key): mixed
     {
-        return $_SESSION[$this->prefix($key)];
+        $key = $this->prefix($key);
+        if (isset($_SESSION[$key]))
+        {
+            return $_SESSION[$key];
+        }
+        return null;
     }
 }