diff --git a/system/src/Grav/Common/GPM/Installer.php b/system/src/Grav/Common/GPM/Installer.php
index caf6bc1a5..cd5116383 100644
--- a/system/src/Grav/Common/GPM/Installer.php
+++ b/system/src/Grav/Common/GPM/Installer.php
@@ -523,7 +523,7 @@ class Installer
 
     /**
      * Returns the last error code of the occurred error
-     * @return int The code of the last error
+     * @return int|string The code of the last error
      */
     public static function lastErrorCode()
     {
diff --git a/system/src/Grav/Framework/Object/Access/NestedPropertyTrait.php b/system/src/Grav/Framework/Object/Access/NestedPropertyTrait.php
index 9dff34b57..1896f47a5 100644
--- a/system/src/Grav/Framework/Object/Access/NestedPropertyTrait.php
+++ b/system/src/Grav/Framework/Object/Access/NestedPropertyTrait.php
@@ -38,8 +38,8 @@ trait NestedPropertyTrait
     public function getNestedProperty($property, $default = null, $separator = null)
     {
         $separator = $separator ?: '.';
-        $path = explode($separator, $property);
-        $offset = array_shift($path);
+        $path = explode($separator, $property) ?: [];
+        $offset = array_shift($path) ?? '';
 
         if (!$this->hasProperty($offset)) {
             return $default;
@@ -81,8 +81,8 @@ trait NestedPropertyTrait
     public function setNestedProperty($property, $value, $separator = null)
     {
         $separator = $separator ?: '.';
-        $path = explode($separator, $property);
-        $offset = array_shift($path);
+        $path = explode($separator, $property) ?: [];
+        $offset = array_shift($path) ?? '';
 
         if (!$path) {
             $this->setProperty($offset, $value);
@@ -123,8 +123,8 @@ trait NestedPropertyTrait
     public function unsetNestedProperty($property, $separator = null)
     {
         $separator = $separator ?: '.';
-        $path = explode($separator, $property);
-        $offset = array_shift($path);
+        $path = explode($separator, $property) ?: [];
+        $offset = array_shift($path) ?? '';
 
         if (!$path) {
             $this->unsetProperty($offset);
diff --git a/system/src/Grav/Framework/Object/Base/ObjectCollectionTrait.php b/system/src/Grav/Framework/Object/Base/ObjectCollectionTrait.php
index 21b7112d5..7e71d9199 100644
--- a/system/src/Grav/Framework/Object/Base/ObjectCollectionTrait.php
+++ b/system/src/Grav/Framework/Object/Base/ObjectCollectionTrait.php
@@ -46,7 +46,7 @@ trait ObjectCollectionTrait
 
     /**
      * @param string $property      Object property to be matched.
-     * @return array                Key/Value pairs of the properties.
+     * @return bool[]               Key/Value pairs of the properties.
      */
     public function doHasProperty($property)
     {
@@ -63,7 +63,7 @@ trait ObjectCollectionTrait
     /**
      * @param string $property      Object property to be fetched.
      * @param mixed $default        Default value if not set.
-     * @return array                Key/Value pairs of the properties.
+     * @return mixed[]              Key/Value pairs of the properties.
      */
     public function doGetProperty($property, $default = null)
     {
@@ -79,7 +79,7 @@ trait ObjectCollectionTrait
 
     /**
      * @param string $property  Object property to be updated.
-     * @param string $value     New value.
+     * @param mixed  $value     New value.
      * @return $this
      */
     public function doSetProperty($property, $value)
@@ -108,7 +108,7 @@ trait ObjectCollectionTrait
 
     /**
      * @param string $property  Object property to be updated.
-     * @param string $default   Default value.
+     * @param mixed  $default   Default value.
      * @return $this
      */
     public function doDefProperty($property, $default)
@@ -124,15 +124,19 @@ trait ObjectCollectionTrait
     /**
      * @param string $method        Method name.
      * @param array  $arguments     List of arguments passed to the function.
-     * @return array                Return values.
+     * @return mixed[]              Return values.
      */
     public function call($method, array $arguments = [])
     {
         $list = [];
 
+        /**
+         * @var string|int $id
+         * @var ObjectInterface $element
+         */
         foreach ($this->getIterator() as $id => $element) {
-            $list[$id] = method_exists($element, $method)
-                ? \call_user_func_array([$element, $method], $arguments) : null;
+            $callable = method_exists($element, $method) ? [$element, $method] : null;
+            $list[$id] = $callable ? \call_user_func_array($callable, $arguments) : null;
         }
 
         return $list;
diff --git a/system/src/Grav/Framework/Object/Base/ObjectTrait.php b/system/src/Grav/Framework/Object/Base/ObjectTrait.php
index 519d4dca7..baeeb2bb7 100644
--- a/system/src/Grav/Framework/Object/Base/ObjectTrait.php
+++ b/system/src/Grav/Framework/Object/Base/ObjectTrait.php
@@ -66,7 +66,7 @@ trait ObjectTrait
 
     /**
      * @param string $property      Object property name.
-     * @return bool                 True if property has been defined (can be null).
+     * @return bool|bool[]          True if property has been defined (can be null).
      */
     public function hasProperty($property)
     {
@@ -76,7 +76,7 @@ trait ObjectTrait
     /**
      * @param string $property      Object property to be fetched.
      * @param mixed $default        Default value if property has not been set.
-     * @return mixed                Property value.
+     * @return mixed|mixed[]        Property value.
      */
     public function getProperty($property, $default = null)
     {
diff --git a/system/src/Grav/Framework/Object/Interfaces/NestedObjectInterface.php b/system/src/Grav/Framework/Object/Interfaces/NestedObjectInterface.php
index 90e6dc935..8d6025a32 100644
--- a/system/src/Grav/Framework/Object/Interfaces/NestedObjectInterface.php
+++ b/system/src/Grav/Framework/Object/Interfaces/NestedObjectInterface.php
@@ -10,47 +10,47 @@
 namespace Grav\Framework\Object\Interfaces;
 
 /**
- * Object Interface
+ * Common Interface for both Objects and Collections
  * @package Grav\Framework\Object
  */
 interface NestedObjectInterface extends ObjectInterface
 {
     /**
-     * @param string $property      Object property name.
-     * @param string $separator     Separator, defaults to '.'
-     * @return bool                 True if property has been defined (can be null).
+     * @param  string       $property   Object property name.
+     * @param  string|null  $separator  Separator, defaults to '.'
+     * @return bool|bool[]              True if property has been defined (can be null).
      */
     public function hasNestedProperty($property, $separator = null);
 
     /**
-     * @param string $property      Object property to be fetched.
-     * @param mixed $default        Default value if property has not been set.
-     * @param string $separator     Separator, defaults to '.'
-     * @return mixed                Property value.
+     * @param  string       $property   Object property to be fetched.
+     * @param  mixed|null   $default    Default value if property has not been set.
+     * @param  string|null  $separator  Separator, defaults to '.'
+     * @return mixed|mixed[]            Property value.
      */
     public function getNestedProperty($property, $default = null, $separator = null);
 
     /**
-     * @param string $property      Object property to be updated.
-     * @param string $value         New value.
-     * @param string $separator     Separator, defaults to '.'
+     * @param  string       $property    Object property to be updated.
+     * @param  mixed        $value       New value.
+     * @param  string|null  $separator   Separator, defaults to '.'
      * @return $this
      * @throws \RuntimeException
      */
     public function setNestedProperty($property, $value, $separator = null);
 
     /**
-     * @param string $property      Object property to be defined.
-     * @param string $default       Default value.
-     * @param string $separator     Separator, defaults to '.'
+     * @param  string $property         Object property to be defined.
+     * @param  mixed  $default          Default value.
+     * @param  string|null $separator   Separator, defaults to '.'
      * @return $this
      * @throws \RuntimeException
      */
     public function defNestedProperty($property, $default, $separator = null);
 
     /**
-     * @param string $property      Object property to be unset.
-     * @param string $separator     Separator, defaults to '.'
+     * @param  string       $property   Object property to be unset.
+     * @param  string|null  $separator  Separator, defaults to '.'
      * @return $this
      * @throws \RuntimeException
      */
diff --git a/system/src/Grav/Framework/Object/Interfaces/ObjectCollectionInterface.php b/system/src/Grav/Framework/Object/Interfaces/ObjectCollectionInterface.php
index fc65f4406..7323294b1 100644
--- a/system/src/Grav/Framework/Object/Interfaces/ObjectCollectionInterface.php
+++ b/system/src/Grav/Framework/Object/Interfaces/ObjectCollectionInterface.php
@@ -36,13 +36,6 @@ interface ObjectCollectionInterface extends CollectionInterface, Selectable, Obj
      */
     public function getObjectKeys();
 
-    /**
-     * @param string $property      Object property to be fetched.
-     * @param mixed $default        Default value if not set.
-     * @return array                Property value.
-     */
-    public function getProperty($property, $default = null);
-
     /**
      * @param string $name          Method name.
      * @param array  $arguments     List of arguments passed to the function.
diff --git a/system/src/Grav/Framework/Object/Interfaces/ObjectInterface.php b/system/src/Grav/Framework/Object/Interfaces/ObjectInterface.php
index 475c5dc04..88c80ab66 100644
--- a/system/src/Grav/Framework/Object/Interfaces/ObjectInterface.php
+++ b/system/src/Grav/Framework/Object/Interfaces/ObjectInterface.php
@@ -26,34 +26,34 @@ interface ObjectInterface extends \Serializable, \JsonSerializable
     public function getKey();
 
     /**
-     * @param string $property      Object property name.
-     * @return bool                 True if property has been defined (can be null).
+     * @param  string       $property   Object property name.
+     * @return bool|bool[]              True if property has been defined (can be null).
      */
     public function hasProperty($property);
 
     /**
-     * @param string $property      Object property to be fetched.
-     * @param mixed $default        Default value if property has not been set.
-     * @return mixed                Property value.
+     * @param  string       $property   Object property to be fetched.
+     * @param  mixed|null   $default    Default value if property has not been set.
+     * @return mixed|mixed[]            Property value.
      */
     public function getProperty($property, $default = null);
 
     /**
-     * @param string $property      Object property to be updated.
-     * @param string $value         New value.
+     * @param  string   $property      Object property to be updated.
+     * @param  mixed    $value         New value.
      * @return $this
      */
     public function setProperty($property, $value);
 
     /**
-     * @param string  $property     Object property to be defined.
-     * @param mixed   $default      Default value.
+     * @param  string  $property        Object property to be defined.
+     * @param  mixed   $default         Default value.
      * @return $this
      */
     public function defProperty($property, $default);
 
     /**
-     * @param string  $property     Object property to be unset.
+     * @param  string  $property     Object property to be unset.
      * @return $this
      */
     public function unsetProperty($property);
diff --git a/system/src/Grav/Framework/Object/ObjectCollection.php b/system/src/Grav/Framework/Object/ObjectCollection.php
index b1670fdfc..e0216aa1a 100644
--- a/system/src/Grav/Framework/Object/ObjectCollection.php
+++ b/system/src/Grav/Framework/Object/ObjectCollection.php
@@ -36,7 +36,7 @@ class ObjectCollection extends ArrayCollection implements ObjectCollectionInterf
     {
         parent::__construct($this->setElements($elements));
 
-        $this->setKey($key);
+        $this->setKey($key ?? '');
     }
 
     /**
@@ -76,11 +76,17 @@ class ObjectCollection extends ArrayCollection implements ObjectCollectionInterf
 
         if ($orderings = $criteria->getOrderings()) {
             $next = null;
+            /**
+             * @var string $field
+             * @var string $ordering
+             */
             foreach (array_reverse($orderings) as $field => $ordering) {
                 $next = ObjectExpressionVisitor::sortByField($field, $ordering === Criteria::DESC ? -1 : 1, $next);
             }
 
-            uasort($filtered, $next);
+            if ($next) {
+                uasort($filtered, $next);
+            }
         }
 
         $offset = $criteria->getFirstResult();
diff --git a/system/src/Grav/Framework/Object/ObjectIndex.php b/system/src/Grav/Framework/Object/ObjectIndex.php
index 16453e983..4ba9b75e6 100644
--- a/system/src/Grav/Framework/Object/ObjectIndex.php
+++ b/system/src/Grav/Framework/Object/ObjectIndex.php
@@ -68,7 +68,7 @@ abstract class ObjectIndex extends AbstractIndexCollection implements ObjectColl
 
     /**
      * @param string $property      Object property name.
-     * @return bool                 True if property has been defined (can be null).
+     * @return array                True if property has been defined (can be null).
      */
     public function hasProperty($property)
     {
@@ -78,7 +78,7 @@ abstract class ObjectIndex extends AbstractIndexCollection implements ObjectColl
     /**
      * @param string $property      Object property to be fetched.
      * @param mixed $default        Default value if property has not been set.
-     * @return mixed                Property value.
+     * @return array                Property values.
      */
     public function getProperty($property, $default = null)
     {
diff --git a/system/src/Grav/Framework/Object/Property/ArrayPropertyTrait.php b/system/src/Grav/Framework/Object/Property/ArrayPropertyTrait.php
index 3606386db..2673f0c40 100644
--- a/system/src/Grav/Framework/Object/Property/ArrayPropertyTrait.php
+++ b/system/src/Grav/Framework/Object/Property/ArrayPropertyTrait.php
@@ -32,7 +32,7 @@ trait ArrayPropertyTrait
     public function __construct(array $elements = [], $key = null)
     {
         $this->setElements($elements);
-        $this->setKey($key);
+        $this->setKey($key ?? '');
     }
 
     /**
diff --git a/system/src/Grav/Framework/Object/Property/ObjectPropertyTrait.php b/system/src/Grav/Framework/Object/Property/ObjectPropertyTrait.php
index cd7bca4b9..efc0c7f05 100644
--- a/system/src/Grav/Framework/Object/Property/ObjectPropertyTrait.php
+++ b/system/src/Grav/Framework/Object/Property/ObjectPropertyTrait.php
@@ -38,7 +38,7 @@ trait ObjectPropertyTrait
     {
         $this->initObjectProperties();
         $this->setElements($elements);
-        $this->setKey($key);
+        $this->setKey($key ?? '');
     }
 
     /**
diff --git a/system/src/Grav/Framework/Pagination/AbstractPagination.php b/system/src/Grav/Framework/Pagination/AbstractPagination.php
index 54a2f60d3..acdad77bf 100644
--- a/system/src/Grav/Framework/Pagination/AbstractPagination.php
+++ b/system/src/Grav/Framework/Pagination/AbstractPagination.php
@@ -17,10 +17,10 @@ class AbstractPagination implements PaginationInterface
     /** @var Route Base rouse used for the pagination. */
     protected $route;
 
-    /** @var int  Current page. */
+    /** @var int|null  Current page. */
     protected $page;
 
-    /** @var int  The record number to start displaying from. */
+    /** @var int|null  The record number to start displaying from. */
     protected $start;
 
     /** @var int  Number of records to display per page. */
diff --git a/system/src/Grav/Framework/RequestHandler/Middlewares/Exceptions.php b/system/src/Grav/Framework/RequestHandler/Middlewares/Exceptions.php
index 8801b1512..568b89a6b 100644
--- a/system/src/Grav/Framework/RequestHandler/Middlewares/Exceptions.php
+++ b/system/src/Grav/Framework/RequestHandler/Middlewares/Exceptions.php
@@ -35,7 +35,10 @@ class Exceptions implements MiddlewareInterface
                 ]
             ];
 
-            return new Response($exception->getCode() ?: 500, [], json_encode($response));
+            /** @var string $json */
+            $json = json_encode($response);
+
+            return new Response($exception->getCode() ?: 500, [], $json);
         }
     }
 }
diff --git a/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php b/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php
index 2de870fc8..153d1a160 100644
--- a/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php
+++ b/system/src/Grav/Framework/RequestHandler/Traits/RequestHandlerTrait.php
@@ -19,13 +19,13 @@ use Psr\Http\Server\MiddlewareInterface;
 
 trait RequestHandlerTrait
 {
-    /** @var string[]|MiddlewareInterface[]|array */
+    /** @var array<string|MiddlewareInterface> */
     protected $middleware;
 
     /** @var callable */
     private $handler;
 
-    /** @var ContainerInterface */
+    /** @var ContainerInterface|null */
     private $container;
 
     /**
@@ -45,7 +45,7 @@ trait RequestHandlerTrait
             return $middleware->process($request, clone $this);
         }
 
-        if (!$this->container || !$this->container->has($middleware)) {
+        if (null === $this->container || !$this->container->has($middleware)) {
             throw new InvalidArgumentException(
                 sprintf('The middleware is not a valid %s and is not passed in the Container', MiddlewareInterface::class),
                 $middleware
diff --git a/system/src/Grav/Framework/Route/RouteFactory.php b/system/src/Grav/Framework/Route/RouteFactory.php
index ac9efcdd0..6b3414a48 100644
--- a/system/src/Grav/Framework/Route/RouteFactory.php
+++ b/system/src/Grav/Framework/Route/RouteFactory.php
@@ -73,7 +73,7 @@ class RouteFactory
 
     public static function setParamValueDelimiter($delimiter)
     {
-        self::$delimiter = $delimiter;
+        self::$delimiter = $delimiter ?: ':';
     }
 
     /**
@@ -134,13 +134,21 @@ class RouteFactory
      */
     public static function parseParams($str)
     {
+        if ($str === '') {
+            return [];
+        }
+
         $delimiter = self::$delimiter;
 
+        /** @var array $params */
         $params = explode('/', $str);
         foreach ($params as &$param) {
+            /** @var array $parts */
             $parts = explode($delimiter, $param, 2);
             if (isset($parts[1])) {
-                $param[rawurldecode($parts[0])] = rawurldecode($parts[1]);
+                $var = rawurldecode($parts[0]);
+                $val = rawurldecode($parts[1]);
+                $param = [$var => $val];
             }
         }
 
diff --git a/system/src/Grav/Framework/Uri/UriFactory.php b/system/src/Grav/Framework/Uri/UriFactory.php
index acbdfa6e5..e5cb1d319 100644
--- a/system/src/Grav/Framework/Uri/UriFactory.php
+++ b/system/src/Grav/Framework/Uri/UriFactory.php
@@ -126,9 +126,9 @@ class UriFactory
             $url
         );
 
-        $parts = parse_url($encodedUrl);
+        $parts = \is_string($encodedUrl) ? parse_url($encodedUrl) : false;
         if ($parts === false) {
-            throw new \InvalidArgumentException('Malformed URL: ' . $encodedUrl);
+            throw new \InvalidArgumentException("Malformed URL: {$url}");
         }
 
         return $parts;
@@ -155,6 +155,12 @@ class UriFactory
      */
     public static function buildQuery(array $params)
     {
-        return $params ? http_build_query($params,  null, ini_get('arg_separator.output'), PHP_QUERY_RFC3986) : '';
+        if (!$params) {
+            return '';
+        }
+
+        $separator = ini_get('arg_separator.output') ?: '&';
+
+        return http_build_query($params, '', $separator, PHP_QUERY_RFC3986);
     }
 }
diff --git a/system/src/Grav/Framework/Uri/UriPartsFilter.php b/system/src/Grav/Framework/Uri/UriPartsFilter.php
index 13063b2c5..88fe3e64e 100644
--- a/system/src/Grav/Framework/Uri/UriPartsFilter.php
+++ b/system/src/Grav/Framework/Uri/UriPartsFilter.php
@@ -50,7 +50,7 @@ class UriPartsFilter
                 return rawurlencode($match[0]);
             },
             $info
-        );
+        ) ?? '';
     }
 
     /**
@@ -114,7 +114,7 @@ class UriPartsFilter
                 return rawurlencode($match[0]);
             },
             $path
-        );
+        ) ?? '';
     }
 
     /**
@@ -136,6 +136,6 @@ class UriPartsFilter
                 return rawurlencode($match[0]);
             },
             $query
-        );
+        ) ?? '';
     }
 }