diff --git a/app/Mage.php b/app/Mage.php
index da389ece420..e504652df00 100644
--- a/app/Mage.php
+++ b/app/Mage.php
@@ -68,49 +68,49 @@ final class Mage
      *
      * @var array
      */
-    static private $_registry                   = [];
+    private static $_registry                   = [];
 
     /**
      * Application root absolute path
      *
      * @var string
      */
-    static private $_appRoot;
+    private static $_appRoot;
 
     /**
      * Application model
      *
      * @var Mage_Core_Model_App
      */
-    static private $_app;
+    private static $_app;
 
     /**
      * Config Model
      *
      * @var Mage_Core_Model_Config
      */
-    static private $_config;
+    private static $_config;
 
     /**
      * Event Collection Object
      *
      * @var Varien_Event_Collection
      */
-    static private $_events;
+    private static $_events;
 
     /**
      * Object cache instance
      *
      * @var Varien_Object_Cache
      */
-    static private $_objects;
+    private static $_objects;
 
     /**
      * Is developer mode flag
      *
      * @var bool
      */
-    static private $_isDeveloperMode            = false;
+    private static $_isDeveloperMode            = false;
 
     /**
      * Is allow throw Exception about headers already sent
@@ -124,7 +124,7 @@ final class Mage
      *
      * @var bool
      */
-    static private $_isInstalled;
+    private static $_isInstalled;
 
     /**
      * Magento edition constants
@@ -140,7 +140,7 @@ final class Mage
      * @var string
      * @static
      */
-    static private $_currentEdition = self::EDITION_COMMUNITY;
+    private static $_currentEdition = self::EDITION_COMMUNITY;
 
     /**
      * Gets the current Magento version string
@@ -182,9 +182,9 @@ public static function getOpenMageVersion()
     {
         $i = self::getOpenMageVersionInfo();
         $versionString = "{$i['major']}.{$i['minor']}.{$i['patch']}";
-        if ( $i['stability'] || $i['number'] ) {
+        if ($i['stability'] || $i['number']) {
             $versionString .= "-";
-            if ( $i['stability'] && $i['number'] ) {
+            if ($i['stability'] && $i['number']) {
                 $versionString .= implode('.', [$i['stability'], $i['number']]);
             } else {
                 $versionString .= implode('', [$i['stability'], $i['number']]);
@@ -240,7 +240,7 @@ public static function getOpenMageVersionInfo()
      */
     public static function getEdition()
     {
-       return self::$_currentEdition;
+        return self::$_currentEdition;
     }
 
     /**
@@ -508,7 +508,7 @@ public static function dispatchEvent($name, array $data = [])
      *
      * @link    Mage_Core_Model_Config::getModelInstance
      * @param   string $modelClass
-     * @param   array|object $arguments
+     * @param   array|string|object $arguments
      * @return  Mage_Core_Model_Abstract|false
      */
     public static function getModel($modelClass = '', $arguments = [])
@@ -845,8 +845,7 @@ public static function log($message, $level = null, $file = '', $forceLog = fals
             if (empty($file)) {
                 $file = self::getStoreConfig('dev/log/file');
             }
-        }
-        catch (Exception $e) {
+        } catch (Exception $e) {
             $logActive = true;
         }
 
@@ -878,7 +877,7 @@ public static function log($message, $level = null, $file = '', $forceLog = fals
                     ',',
                     (string) self::getConfig()->getNode('dev/log/allowedFileExtensions', Mage_Core_Model_Store::DEFAULT_CODE)
                 );
-                if ( ! ($extension = pathinfo($file, PATHINFO_EXTENSION)) || ! in_array($extension, $_allowedFileExtensions)) {
+                if (! ($extension = pathinfo($file, PATHINFO_EXTENSION)) || ! in_array($extension, $_allowedFileExtensions)) {
                     return;
                 }
 
@@ -900,8 +899,7 @@ public static function log($message, $level = null, $file = '', $forceLog = fals
                 $writerModel = (string)self::getConfig()->getNode('global/log/core/writer_model');
                 if (!self::$_app || !$writerModel) {
                     $writer = new Zend_Log_Writer_Stream($logFile);
-                }
-                else {
+                } else {
                     $writer = new $writerModel($logFile);
                 }
                 $writer->setFormatter($formatter);
@@ -914,8 +912,7 @@ public static function log($message, $level = null, $file = '', $forceLog = fals
 
             $message = addcslashes($message, '<?');
             $loggers[$file]->log($message, $level);
-        }
-        catch (Exception $e) {
+        } catch (Exception $e) {
         }
     }
 
@@ -973,7 +970,6 @@ public static function printException(Throwable $e, $extra = '')
             print $e->getTraceAsString();
             print '</pre>';
         } else {
-
             $reportData = [
                 (!empty($extra) ? $extra . "\n\n" : '') . $e->getMessage(),
                 $e->getTraceAsString()
@@ -993,8 +989,8 @@ public static function printException(Throwable $e, $extra = '')
             try {
                 $storeCode = self::app()->getStore()->getCode();
                 $reportData['skin'] = $storeCode;
+            } catch (Exception $e) {
             }
-            catch (Exception $e) {}
 
             require_once(self::getBaseDir() . DS . 'errors' . DS . 'report.php');
         }
@@ -1059,6 +1055,5 @@ public static function getScriptSystemUrl($folder, $exitIfNot = false)
      */
     public static function setIsDownloader()
     {
-
     }
 }
diff --git a/app/code/core/Mage/Admin/Model/Config.php b/app/code/core/Mage/Admin/Model/Config.php
index 35bc407bfbf..f8549e41174 100644
--- a/app/code/core/Mage/Admin/Model/Config.php
+++ b/app/code/core/Mage/Admin/Model/Config.php
@@ -43,7 +43,6 @@ public function __construct()
         parent::__construct();
         $this->setCacheId('adminhtml_acl_menu_config');
 
-        /** @var Varien_Simplexml_Config $adminhtmlConfig */
         $adminhtmlConfig = Mage::app()->loadCache($this->getCacheId());
         if ($adminhtmlConfig) {
             $this->_adminhtmlConfig = new Varien_Simplexml_Config($adminhtmlConfig);
@@ -80,7 +79,7 @@ public function __construct()
      * Load Acl resources from config
      *
      * @param Mage_Admin_Model_Acl $acl
-     * @param Mage_Core_Model_Config_Element $resource
+     * @param Mage_Core_Model_Config_Element|Varien_Simplexml_Element $resource
      * @param string $parentName
      * @return $this
      */
diff --git a/app/code/core/Mage/Admin/Model/Observer.php b/app/code/core/Mage/Admin/Model/Observer.php
index f98f45333ae..d697fb194de 100644
--- a/app/code/core/Mage/Admin/Model/Observer.php
+++ b/app/code/core/Mage/Admin/Model/Observer.php
@@ -70,7 +70,7 @@ public function actionPreDispatchAdmin($observer)
                         $session->login($username, $password, $request);
                         $request->setPost('login', null);
                     } else {
-                        if ($request && !$request->getParam('messageSent')) {
+                        if (!$request->getParam('messageSent')) {
                             Mage::getSingleton('adminhtml/session')->addError(
                                 Mage::helper('adminhtml')->__('Invalid Form Key. Please refresh the page.')
                             );
diff --git a/app/code/core/Mage/Admin/Model/Session.php b/app/code/core/Mage/Admin/Model/Session.php
index 76d287627c5..cba417c24ad 100644
--- a/app/code/core/Mage/Admin/Model/Session.php
+++ b/app/code/core/Mage/Admin/Model/Session.php
@@ -63,7 +63,7 @@ class Mage_Admin_Model_Session extends Mage_Core_Model_Session_Abstract
     /**
      * Whether it is the first page after successfull login
      *
-     * @var bool
+     * @var bool|null
      */
     protected $_isFirstPageAfterLogin;
 
diff --git a/app/code/core/Mage/Admin/Model/User.php b/app/code/core/Mage/Admin/Model/User.php
index c2bedf1c450..de9520a0582 100644
--- a/app/code/core/Mage/Admin/Model/User.php
+++ b/app/code/core/Mage/Admin/Model/User.php
@@ -504,7 +504,7 @@ protected function _getHelper($helperName)
     /**
      * Find first menu item that user is able to access
      *
-     * @param Mage_Core_Model_Config_Element $parent
+     * @param Mage_Core_Model_Config_Element|Varien_Simplexml_Element $parent
      * @param string $path
      * @param int $level
      * @return string
diff --git a/app/code/core/Mage/AdminNotification/Model/Feed.php b/app/code/core/Mage/AdminNotification/Model/Feed.php
index 6f5d8e84cae..6260412f5ed 100644
--- a/app/code/core/Mage/AdminNotification/Model/Feed.php
+++ b/app/code/core/Mage/AdminNotification/Model/Feed.php
@@ -120,7 +120,7 @@ public function getFrequency()
     /**
      * Retrieve Last update time
      *
-     * @return int
+     * @return string|false
      */
     public function getLastUpdate()
     {
diff --git a/app/code/core/Mage/Core/Model/App.php b/app/code/core/Mage/Core/Model/App.php
index 4ae3a039af5..7cba35203a6 100644
--- a/app/code/core/Mage/Core/Model/App.php
+++ b/app/code/core/Mage/Core/Model/App.php
@@ -1162,7 +1162,7 @@ public function getCache()
      * Loading cache data
      *
      * @param   string $id
-     * @return  mixed
+     * @return  string|false
      */
     public function loadCache($id)
     {
diff --git a/app/code/core/Mage/Core/Model/Cache.php b/app/code/core/Mage/Core/Model/Cache.php
index 695453c78a2..43f56c6ea73 100644
--- a/app/code/core/Mage/Core/Model/Cache.php
+++ b/app/code/core/Mage/Core/Model/Cache.php
@@ -366,7 +366,7 @@ public function getFrontend()
      * Load data from cache by id
      *
      * @param   string $id
-     * @return  string
+     * @return  string|false
      */
     public function load($id)
     {
diff --git a/app/code/core/Mage/Core/Model/Config.php b/app/code/core/Mage/Core/Model/Config.php
index 87fa1981bc6..f98dd818c12 100644
--- a/app/code/core/Mage/Core/Model/Config.php
+++ b/app/code/core/Mage/Core/Model/Config.php
@@ -1013,9 +1013,9 @@ public function determineOmittedNamespace($name, $asFullModuleName = false)
      * specidied xml file name to one object
      *
      * @param string $fileName
-     * @param null|Mage_Core_Model_Config_Base $mergeToObject
+     * @param null|Mage_Core_Model_Config_Base|Varien_Simplexml_Config $mergeToObject
      * @param null $mergeModel
-     * @return Mage_Core_Model_Config_Base
+     * @return Mage_Core_Model_Config_Base|Varien_Simplexml_Config
      */
     public function loadModulesConfiguration($fileName, $mergeToObject = null, $mergeModel = null)
     {
diff --git a/app/code/core/Mage/Log/Model/Visitor/Online.php b/app/code/core/Mage/Log/Model/Visitor/Online.php
index 2d7aeab0242..2d19ff23522 100644
--- a/app/code/core/Mage/Log/Model/Visitor/Online.php
+++ b/app/code/core/Mage/Log/Model/Visitor/Online.php
@@ -66,7 +66,7 @@ public function prepare()
     /**
      * Retrieve last prepare at timestamp
      *
-     * @return int
+     * @return string|false
      */
     public function getPrepareAt()
     {
diff --git a/index.php b/index.php
index dfb0bf13c44..99a912924ad 100644
--- a/index.php
+++ b/index.php
@@ -55,10 +55,10 @@
 umask(0);
 
 /* Store or website code */
-$mageRunCode = isset($_SERVER['MAGE_RUN_CODE']) ? $_SERVER['MAGE_RUN_CODE'] : '';
+$mageRunCode = $_SERVER['MAGE_RUN_CODE'] ?? '';
 
 /* Run store or run website */
-$mageRunType = isset($_SERVER['MAGE_RUN_TYPE']) ? $_SERVER['MAGE_RUN_TYPE'] : 'store';
+$mageRunType = $_SERVER['MAGE_RUN_TYPE'] ?? 'store';
 
 if (file_exists($maintenanceFile)) {
     $maintenanceBypass = false;
diff --git a/lib/Varien/Cache/Core.php b/lib/Varien/Cache/Core.php
index ddaaa298df2..c75775c2e68 100644
--- a/lib/Varien/Cache/Core.php
+++ b/lib/Varien/Cache/Core.php
@@ -155,7 +155,7 @@ public function load($id, $doNotTestCacheValidity = false, $doNotUnserialize = f
             // Seems we've got chunked data
 
             $arr = explode('|', $data);
-            $chunks = isset($arr[1]) ? $arr[1] : false;
+            $chunks = $arr[1] ?? false;
             $chunkData = [];
 
             if ($chunks && is_numeric($chunks)) {