diff --git a/.gitignore b/.gitignore
index 57872d0..0dca145 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
 /vendor/
+.idea
diff --git a/composer.json b/composer.json
index 6278274..b6bcd51 100644
--- a/composer.json
+++ b/composer.json
@@ -10,14 +10,15 @@
         }
     ],
     "autoload": {
-        "classmap": [
-            "src/"
-        ]
+        "psr-4": {
+            "Gorse\\": "src/"
+        }
     },
     "require-dev": {
         "phpunit/phpunit": "^9.3"
     },
     "require": {
+        "php": "~8.2.0 || ~8.3.0",
         "guzzlehttp/guzzle": "^7.0",
         "ext-redis": "*"
     }
diff --git a/src/Feedback.php b/src/Feedback.php
new file mode 100644
index 0000000..cbd2de4
--- /dev/null
+++ b/src/Feedback.php
@@ -0,0 +1,31 @@
+<?php declare(strict_types=1);
+
+namespace Gorse;
+
+readonly class Feedback implements \JsonSerializable
+{
+    public function __construct(
+        public string $feedbackType,
+        public string $userId,
+        public string $itemId,
+        public string $timestamp,
+        public ?string $comment = null,
+    ) {
+    }
+
+    public function jsonSerialize(): array
+    {
+        $result = [
+            'FeedbackType' => $this->feedbackType,
+            'UserId' => $this->userId,
+            'ItemId' => $this->itemId,
+            'Timestamp' => $this->timestamp,
+        ];
+
+        if ($this->comment) {
+            $result['Comment'] = $this->comment;
+        }
+
+        return $result;
+    }
+}
\ No newline at end of file
diff --git a/src/Gorse.php b/src/Gorse.php
index cd16322..fef658c 100644
--- a/src/Gorse.php
+++ b/src/Gorse.php
@@ -1,79 +1,15 @@
-<?php
+<?php declare(strict_types=1);
 
-use GuzzleHttp\Exception\GuzzleException;
-
-class User implements JsonSerializable
-{
-    public string $userId;
-    public array $labels;
-
-    public function __construct(string $userId, array $labels)
-    {
-        $this->userId = $userId;
-        $this->labels = $labels;
-    }
-
-    public function jsonSerialize(): array
-    {
-        return [
-            'UserId' => $this->userId,
-            'Labels' => $this->labels,
-        ];
-    }
-
-    public static function fromJSON($json): User
-    {
-        return new User($json->UserId, $json->Labels);
-    }
-}
-
-class Feedback implements JsonSerializable
-{
-    public string $feedback_type;
-    public string $user_id;
-    public string $item_id;
-    public string $timestamp;
-
-    public function __construct(string $feedback_type, string $user_id, string $item_id, string $timestamp)
-    {
-        $this->feedback_type = $feedback_type;
-        $this->user_id = $user_id;
-        $this->item_id = $item_id;
-        $this->timestamp = $timestamp;
-    }
-
-    public function jsonSerialize(): array
-    {
-        return [
-            'FeedbackType' => $this->feedback_type,
-            'UserId' => $this->user_id,
-            'ItemId' => $this->item_id,
-            'Timestamp' => $this->timestamp,
-        ];
-    }
-}
-
-class RowAffected
-{
-    public int $rowAffected;
+namespace Gorse;
 
-    public static function fromJSON($json): RowAffected
-    {
-        $rowAffected = new RowAffected();
-        $rowAffected->rowAffected = $json->RowAffected;
-        return $rowAffected;
-    }
-}
+use GuzzleHttp\Exception\GuzzleException;
 
-final class Gorse
+final readonly class Gorse
 {
-    private string $endpoint;
-    private string $apiKey;
-
-    function __construct(string $endpoint, string $apiKey)
-    {
-        $this->endpoint = $endpoint;
-        $this->apiKey = $apiKey;
+    function __construct(
+        private string $endpoint,
+        private string $apiKey
+    ) {
     }
 
     /**
@@ -87,39 +23,44 @@ function insertUser(User $user): RowAffected
     /**
      * @throws GuzzleException
      */
-    function getUser(string $user_id): User
+    function getUser(string $userId): User
     {
-        return User::fromJSON($this->request('GET', '/api/user/' . $user_id, null));
+        return User::fromJSON($this->request('GET', '/api/user/' . $userId));
     }
 
     /**
      * @throws GuzzleException
      */
-    function deleteUser(string $user_id): RowAffected
+    function deleteUser(string $userId): RowAffected
     {
-        return RowAffected::fromJSON($this->request('DELETE', '/api/user/' . $user_id, null));
+        return RowAffected::fromJSON($this->request('DELETE', '/api/user/' . $userId));
     }
 
     /**
+     * @param Feedback|Feedback[] $feedback
      * @throws GuzzleException
      */
-    function insertFeedback(array $feedback): RowAffected
+    function insertFeedback(mixed $feedback): RowAffected
     {
+        if ($feedback instanceof Feedback) {
+            $feedback = [$feedback];
+        }
+
         return RowAffected::fromJSON($this->request('POST', '/api/feedback/', $feedback));
     }
 
     /**
      * @throws GuzzleException
      */
-    function getRecommend(string $user_id): array
+    function getRecommend(string $userId): array
     {
-        return $this->request('GET', '/api/recommend/' . $user_id, null);
+        return $this->request('GET', '/api/recommend/' . $userId);
     }
 
     /**
      * @throws GuzzleException
      */
-    private function request(string $method, string $uri, $body)
+    private function request(string $method, string $uri, \JsonSerializable|array|null $body = null)
     {
         $client = new GuzzleHttp\Client(['base_uri' => $this->endpoint]);
         $options = [GuzzleHttp\RequestOptions::HEADERS => ['X-API-Key' => $this->apiKey]];
@@ -127,6 +68,7 @@ private function request(string $method, string $uri, $body)
             $options[GuzzleHttp\RequestOptions::JSON] = $body;
         }
         $response = $client->request($method, $uri, $options);
+
         return json_decode($response->getBody());
     }
 }
\ No newline at end of file
diff --git a/src/RowAffected.php b/src/RowAffected.php
new file mode 100644
index 0000000..6d3718d
--- /dev/null
+++ b/src/RowAffected.php
@@ -0,0 +1,16 @@
+<?php declare(strict_types=1);
+
+namespace Gorse;
+
+readonly class RowAffected
+{
+    public function __construct(
+        public int $rowAffected
+    ) {
+    }
+
+    public static function fromJSON(object $json): RowAffected
+    {
+        return new RowAffected($json->RowAffected);
+    }
+}
\ No newline at end of file
diff --git a/src/User.php b/src/User.php
new file mode 100644
index 0000000..152e0dd
--- /dev/null
+++ b/src/User.php
@@ -0,0 +1,26 @@
+<?php declare(strict_types=1);
+
+namespace Gorse;
+
+readonly class User implements \JsonSerializable
+{
+
+    public function __construct(
+        public string $userId,
+        public array $labels
+    ) {
+    }
+
+    public function jsonSerialize(): array
+    {
+        return [
+            'UserId' => $this->userId,
+            'Labels' => $this->labels,
+        ];
+    }
+
+    public static function fromJSON($json): User
+    {
+        return new User($json->UserId, $json->Labels);
+    }
+}
diff --git a/test/GorseTest.php b/test/GorseTest.php
index 25f6469..a76e32b 100644
--- a/test/GorseTest.php
+++ b/test/GorseTest.php
@@ -1,5 +1,8 @@
 <?php
 
+use Gorse\Feedback;
+use Gorse\Gorse;
+use Gorse\User;
 use GuzzleHttp\Exception\ClientException;
 use GuzzleHttp\Exception\GuzzleException;
 use PHPUnit\Framework\TestCase;