diff --git a/Module/NullModule.php b/Module/NullModule.php
index 791afaa64..7f89ad9a9 100755
--- a/Module/NullModule.php
+++ b/Module/NullModule.php
@@ -44,12 +44,4 @@ final class NullModule extends ModuleAbstract
                 ]
             );
     }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function jsonSerialize() : mixed
-    {
-        return ['id' => $this->id];
-    }
 }
diff --git a/Router/SocketRouter.php b/Router/SocketRouter.php
index 1d90ed041..f52bb38a8 100755
--- a/Router/SocketRouter.php
+++ b/Router/SocketRouter.php
@@ -124,7 +124,7 @@ final class SocketRouter implements RouterInterface
      * @param Account $account Account
      * @param array   $data    Data
      *
-     * @return array[]
+     * @return array
      *
      * @since 1.0.0
      */
@@ -149,7 +149,7 @@ final class SocketRouter implements RouterInterface
                     || ($verb & $d['verb']) === $verb
                 ) {
                     // if permission check is invalid
-                    if  (isset($d['permission']) && !empty($d['permission'])
+                    if (isset($d['permission']) && !empty($d['permission'])
                         && ($account === null || $account instanceof NullAccount)
                     ) {
                         return ['dest' => RouteStatus::NOT_LOGGED_IN];
diff --git a/Router/WebRouter.php b/Router/WebRouter.php
index 167058542..ea489c10e 100755
--- a/Router/WebRouter.php
+++ b/Router/WebRouter.php
@@ -129,7 +129,7 @@ final class WebRouter implements RouterInterface
      * @param Account $account Account
      * @param array   $data    Validation
      *
-     * @return array[]
+     * @return array
      *
      * @since 1.0.0
      */
diff --git a/Utils/Parser/Pdf/PdfParser.php b/Utils/Parser/Pdf/PdfParser.php
index 11cf98d92..0f0451ec3 100755
--- a/Utils/Parser/Pdf/PdfParser.php
+++ b/Utils/Parser/Pdf/PdfParser.php
@@ -34,7 +34,7 @@ class PdfParser
      * @var string
      * @var 1.0.0
      */
-    public static $pdftotext = '/usr/bin/pdftotext';
+    public static string $pdftotext = '/usr/bin/pdftotext';
 
     /**
      * PDFToPPM path.
@@ -42,7 +42,7 @@ class PdfParser
      * @var string
      * @var 1.0.0
      */
-    public static $pdftoppm = '/usr/bin/pdftoppm';
+    public static string $pdftoppm = '/usr/bin/pdftoppm';
 
     /**
      * Pdf to text