diff --git a/composer.json b/composer.json
index 17adf3e6..a7e76164 100644
--- a/composer.json
+++ b/composer.json
@@ -80,6 +80,8 @@
     "scripts": {
         "cs:check": "vendor/bin/php-cs-fixer check",
         "cs:fix": "vendor/bin/php-cs-fixer fix",
+        "rector:check": "vendor/bin/rector process --dry-run",
+        "rector:fix": "vendor/bin/rector process",
         "phpstan": "vendor/bin/phpstan analyse --memory-limit=-1 --error-format=github",
         "test": "vendor/bin/phpunit --stderr --testdox --coverage-clover coverage.xml"
     },
diff --git a/src/App/Helpers/misc.php b/src/App/Helpers/misc.php
index f4a333bc..7a90f487 100644
--- a/src/App/Helpers/misc.php
+++ b/src/App/Helpers/misc.php
@@ -22,8 +22,8 @@
 function _message(string $subject, $params): string
 {
     if (is_array($params)) {
-        return preg_replace_callback('/{%\d+}/', function () use (&$params) {
-            return array_shift($params);
+        return preg_replace_callback('/{%\d+}/', function (array $matches) use (&$params): string {
+            return array_shift($params) ?? '';
         }, $subject) ?? $subject;
     } else {
         return preg_replace('/{%\d+}/', $params, $subject) ?? $subject;
diff --git a/src/Environment/Server.php b/src/Environment/Server.php
index 8c270b4d..9cbc50b7 100644
--- a/src/Environment/Server.php
+++ b/src/Environment/Server.php
@@ -69,7 +69,7 @@ public function all(): array
      * @param string $key
      * @return mixed|null
      */
-    public function get($key)
+    public function get(string $key)
     {
         return $this->server[$key] ?? null;
     }
@@ -86,7 +86,7 @@ public function has($key): bool
      * @param string $key
      * @param mixed $value
      */
-    public function set($key, $value): void
+    public function set(string $key, $value): void
     {
         $this->server[$key] = $value;
     }
diff --git a/src/Mailer/Adapters/SmtpAdapter.php b/src/Mailer/Adapters/SmtpAdapter.php
index ba313c03..85c8cee5 100644
--- a/src/Mailer/Adapters/SmtpAdapter.php
+++ b/src/Mailer/Adapters/SmtpAdapter.php
@@ -50,7 +50,7 @@ public function __construct(array $params)
         if (config()->get('debug')) {
             $this->mailer->SMTPDebug = SMTP::DEBUG_SERVER;
 
-            $this->mailer->Debugoutput = function ($message): void {
+            $this->mailer->Debugoutput = function (string $message): void {
                 warning($message, ['tab' => Debugger::MAILS]);
             };
         }
diff --git a/src/Service/Factories/ServiceFactory.php b/src/Service/Factories/ServiceFactory.php
index 8e78578d..b800fbe0 100644
--- a/src/Service/Factories/ServiceFactory.php
+++ b/src/Service/Factories/ServiceFactory.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * Quantum PHP Framework
  *