diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f10d52d6..ee5fd1cb9 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,34 +4,40 @@
 1. [](#new)
     * Added `select()` and `unselect()` methods to `CollectionInterface` and its base classes
     * Added `orderBy()` and `limit()` methods to `ObjectCollectionInterface` and its base classes
-    * Flex: Added support for custom object index classes (API compatibility break)
     * Added `user-data://` which is a writable stream (`user://data` is not and should be avoided)
-    * Added support for `/action:{$action}` (like task but works without nonce, used only for getting data)
+    * Added support for `/action:{$action}` (like task but used without nonce when only receiving data)
     * Added `onAction.{$action}` event
+    * Added `Grav\Framework\Form\FormFlash` class to contain AJAX uploaded files in more reliable way
+    * Added `Grav\Framework\Form\FormFlashFile` class which implements `UploadedFileInterface` from PSR-7
+    * Added `Grav\Framework\Filesystem\Filesystem` class with methods to manipulate stream URLs
+    * Grav 1.6: Flex: Added support for custom object index classes (API compatibility break)
 1. [](#improved)
-    * Improve Flex storage
+    * Improved `Grav\Framework\File\Formatter` classes to have abstract parent class and some useful methods
+    * Grav 1.6: Improved Flex storage classes
+    * Grav 1.6: Improved `Grav\Framework\File` classes to use better type hints and the new `Filesystem` class
 1. [](#bugfix)
     * Fixed handling of `append_url_extension` inside of `Page::templateFormat()` [#2264](https://github.com/getgrav/grav/issues/2264) 
     * Fixed a broken language string [#2261](https://github.com/getgrav/grav/issues/2261)
     * Fixed clearing cache having no effect on Doctrine cache
     * Fixed `Medium::relativePath()` for streams
-    * Fixed `FlexObject::update()` call with partial object update
+    * Fixed `Object` serialization breaking if overriding `jsonSerialize()` method
+    * Grav 1.6: Fixed `FlexObject::update()` call with partial object update
 
 # v1.6.0-beta.6
 ## 11/12/2018
 
 1. [](#new)
-    * Added `CsvFormatter` and `CsvFile` classes
     * Added `$grav->setup()` to simplify CLI and custom access points
+    * Grav 1.6: Added `CsvFormatter` and `CsvFile` classes
 1. [](#improved)
     * Support negotiated content types set via the Request `Accept:` header
     * Support negotiated language types set via the Request `Accept-Language:` header
-    * Allow custom Flex form views
     * Cleaned up and sorted the Service `idMap`
+    * Grav 1.6: Allow custom Flex form views
 1. [](#bugfix)
     * Fixed `Uri::hasStandardPort()` to support reverse proxy configurations [#1786](https://github.com/getgrav/grav/issues/1786)
     * Use `append_url_extension` from page header to set template format if set [#2604](https://github.com/getgrav/grav/pull/2064)
-    * Fixed some bugs in environment selection
+    * Fixed some bugs in Grav environment selection logic
 
 # v1.6.0-beta.5
 ## 11/05/2018
@@ -50,7 +56,7 @@
     * Set session name based on `security.salt` rather than `GRAV_ROOT` [#2242](https://github.com/getgrav/grav/issues/2242)
     * Added option to configure list of `xss_invalid_protocols` in `Security` config [#2250](https://github.com/getgrav/grav/issues/2250)
     * Smarter `security.salt` checking now we use `security.yaml` for other options
-    * Merged Grav 1.5.4 fixes in
+    * Grav 1.6: Merged Grav 1.5.4 fixes in
 
 # v1.6.0-beta.4
 ## 10/24/2018
@@ -79,15 +85,15 @@
 ## 10/09/2018
 
 1. [](#new)
-    * Added Flex support for custom media tasks
+    * Grav 1.6: Added Flex support for custom media tasks
 1. [](#improved)
     * Added support for syslog and syslog facility logging (default: 'file')
     * Improved usability of `System` configuration blueprint with side-tabs
 1. [](#bugfix)
     * Fixed asset manager to not add empty assets when they don't exist in the filesystem
-    * Regression: Fixed asset manager methods with default legacy attributes
     * Update `script` and `style` Twig tags to use the new `Assets` classes
     * Fixed asset pipeline to rewrite remote URLs as well as local [#2216](https://github.com/getgrav/grav/issues/2216)
+    * Grav 1.6: Regression: Fixed asset manager methods with default legacy attributes
 
 # v1.6.0-beta.1
 ## 10/01/2018
diff --git a/system/src/Grav/Framework/DI/Container.php b/system/src/Grav/Framework/DI/Container.php
index ef71a3bb6..8d52cceef 100644
--- a/system/src/Grav/Framework/DI/Container.php
+++ b/system/src/Grav/Framework/DI/Container.php
@@ -20,7 +20,7 @@ class Container extends \Pimple\Container implements ContainerInterface
         return $this->offsetGet($id);
     }
 
-    public function has($id)
+    public function has($id): bool
     {
         return $this->offsetExists($id);
     }
diff --git a/system/src/Grav/Framework/File/AbstractFile.php b/system/src/Grav/Framework/File/AbstractFile.php
index 0023d48ce..9317a6949 100644
--- a/system/src/Grav/Framework/File/AbstractFile.php
+++ b/system/src/Grav/Framework/File/AbstractFile.php
@@ -12,9 +12,13 @@ declare(strict_types=1);
 namespace Grav\Framework\File;
 
 use Grav\Framework\File\Interfaces\FileInterface;
+use Grav\Framework\Filesystem\Filesystem;
 
 class AbstractFile implements FileInterface
 {
+    /** @var Filesystem */
+    private $filesystem;
+
     /** @var string */
     private $filepath;
 
@@ -36,8 +40,13 @@ class AbstractFile implements FileInterface
     /** @var bool */
     private $locked = false;
 
-    public function __construct($filepath)
+    /**
+     * @param string $filepath
+     * @param Filesystem|null $filesystem
+     */
+    public function __construct(string $filepath, Filesystem $filesystem = null)
     {
+        $this->filesystem = $filesystem ?? new Filesystem();
         $this->setFilepath($filepath);
     }
 
@@ -51,11 +60,26 @@ class AbstractFile implements FileInterface
         }
     }
 
-    /**
-     * Prevent cloning.
-     */
-    private function __clone()
+    public function __clone()
     {
+        $this->handle = null;
+        $this->locked = false;
+    }
+
+    /**
+     * @return string
+     */
+    public function serialize(): string
+    {
+        return serialize($this->doSerialize());
+    }
+
+    /**
+     * @param string $serialized
+     */
+    public function unserialize($serialized): void
+    {
+        $this->doUnserialize(unserialize($serialized, ['allowed_classes' => false]));
     }
 
     /**
@@ -63,7 +87,7 @@ class AbstractFile implements FileInterface
      *
      * @return string
      */
-    public function getFilePath() : string
+    public function getFilePath(): string
     {
         return $this->filepath;
     }
@@ -73,7 +97,7 @@ class AbstractFile implements FileInterface
      *
      * @return string
      */
-    public function getPath() : string
+    public function getPath(): string
     {
         if (null === $this->path) {
             $this->setPathInfo();
@@ -87,7 +111,7 @@ class AbstractFile implements FileInterface
      *
      * @return string
      */
-    public function getFilename() : string
+    public function getFilename(): string
     {
         if (null === $this->filename) {
             $this->setPathInfo();
@@ -101,7 +125,7 @@ class AbstractFile implements FileInterface
      *
      * @return string
      */
-    public function getBasename() : string
+    public function getBasename(): string
     {
         if (null === $this->basename) {
             $this->setPathInfo();
@@ -113,10 +137,10 @@ class AbstractFile implements FileInterface
     /**
      * Return file extension.
      *
-     * @param $withDot
+     * @param bool $withDot
      * @return string
      */
-    public function getExtension($withDot = false) : string
+    public function getExtension(bool $withDot = false): string
     {
         if (null === $this->extension) {
             $this->setPathInfo();
@@ -130,7 +154,7 @@ class AbstractFile implements FileInterface
      *
      * @return bool
      */
-    public function exists() : bool
+    public function exists(): bool
     {
         return is_file($this->filepath);
     }
@@ -138,21 +162,21 @@ class AbstractFile implements FileInterface
     /**
      * Return file modification time.
      *
-     * @return int|bool Timestamp or false if file doesn't exist.
+     * @return int Unix timestamp. If file does not exist, method returns current time.
      */
-    public function getCreationTime()
+    public function getCreationTime(): int
     {
-        return is_file($this->filepath) ? filectime($this->filepath) : false;
+        return is_file($this->filepath) ? filectime($this->filepath) : time();
     }
 
     /**
      * Return file modification time.
      *
-     * @return int|bool Timestamp or false if file doesn't exist.
+     * @return int Unix timestamp. If file does not exist, method returns current time.
      */
-    public function getModificationTime()
+    public function getModificationTime(): int
     {
-        return is_file($this->filepath) ? filemtime($this->filepath) : false;
+        return is_file($this->filepath) ? filemtime($this->filepath) : time();
     }
 
     /**
@@ -162,7 +186,7 @@ class AbstractFile implements FileInterface
      * @return bool
      * @throws \RuntimeException
      */
-    public function lock($block = true) : bool
+    public function lock(bool $block = true): bool
     {
         if (!$this->handle) {
             if (!$this->mkdir($this->getPath())) {
@@ -184,7 +208,7 @@ class AbstractFile implements FileInterface
      *
      * @return bool
      */
-    public function unlock() : bool
+    public function unlock(): bool
     {
         if (!$this->handle) {
             return false;
@@ -204,25 +228,39 @@ class AbstractFile implements FileInterface
      *
      * @return bool True = locked, false = not locked.
      */
-    public function isLocked() : bool
+    public function isLocked(): bool
     {
         return $this->locked;
     }
 
+    /**
+     * Check if file exists and can be read.
+     *
+     * @return bool
+     */
+    public function isReadable(): bool
+    {
+        return is_readable($this->filepath) && is_file($this->filepath);
+    }
+
     /**
      * Check if file can be written.
      *
      * @return bool
      */
-    public function isWritable() : bool
+    public function isWritable(): bool
     {
-        return is_writable($this->filepath) || $this->isWritableDir($this->getPath());
+        if (!file_exists($this->filepath)) {
+            return $this->isWritablePath($this->getPath());
+        }
+
+        return is_writable($this->filepath) && is_file($this->filepath);
     }
 
     /**
-     * (Re)Load a file and return RAW file contents.
+     * (Re)Load a file and return file contents.
      *
-     * @return string
+     * @return string|array|false
      */
     public function load()
     {
@@ -235,7 +273,7 @@ class AbstractFile implements FileInterface
      * @param  mixed $data
      * @throws \RuntimeException
      */
-    public function save($data)
+    public function save($data): void
     {
         $lock = false;
         if (!$this->locked) {
@@ -266,7 +304,7 @@ class AbstractFile implements FileInterface
      * @param string $path
      * @return bool
      */
-    public function rename($path) : bool
+    public function rename(string $path): bool
     {
         if ($this->exists() && !@rename($this->filepath, $path)) {
             return false;
@@ -282,7 +320,7 @@ class AbstractFile implements FileInterface
      *
      * @return bool
      */
-    public function delete() : bool
+    public function delete(): bool
     {
         return @unlink($this->filepath);
     }
@@ -293,7 +331,7 @@ class AbstractFile implements FileInterface
      * @throws \RuntimeException
      * @internal
      */
-    protected function mkdir($dir) : bool
+    protected function mkdir(string $dir): bool
     {
         // Silence error for open_basedir; should fail in mkdir instead.
         if (!@is_dir($dir)) {
@@ -310,20 +348,27 @@ class AbstractFile implements FileInterface
     }
 
     /**
-     * @param  string  $dir
-     * @return bool
-     * @internal
+     * @return array
      */
-    protected function isWritableDir($dir) : bool
+    protected function doSerialize(): array
     {
-        if ($dir && !file_exists($dir)) {
-            return $this->isWritableDir(\dirname($dir));
-        }
-
-        return $dir && is_dir($dir) && is_writable($dir);
+        return [
+            'filepath' => $this->filepath
+        ];
     }
 
-    protected function setFilepath($filepath) : void
+    /**
+     * @param array $serialized
+     */
+    protected function doUnserialize(array $serialized): void
+    {
+        $this->setFilepath($serialized['filepath']);
+    }
+
+    /**
+     * @param string $filepath
+     */
+    protected function setFilepath(string $filepath): void
     {
         $this->filepath = $filepath;
         $this->filename = null;
@@ -332,64 +377,32 @@ class AbstractFile implements FileInterface
         $this->extension = null;
     }
 
-    protected function setPathInfo() : void
+    protected function setPathInfo(): void
     {
-        $pathInfo = static::pathinfo($this->filepath);
-        $this->filename = $pathInfo['filename'];
-        $this->basename = $pathInfo['basename'];
-        $this->path = $pathInfo['dirname'];
-        $this->extension = $pathInfo['extension'];
+        $pathInfo = $this->filesystem->pathinfo($this->filepath);
+
+        $this->filename = $pathInfo['filename'] ?? null;
+        $this->basename = $pathInfo['basename'] ?? null;
+        $this->path = $pathInfo['dirname'] ?? null;
+        $this->extension = $pathInfo['extension'] ?? null;
     }
 
     /**
-     * Multi-byte-safe pathinfo replacement.
-     * Replacement for pathinfo(), but stream, multibyte and cross-platform safe.
-     *
-     * @see    http://www.php.net/manual/en/function.pathinfo.php
-     *
-     * @param string     $path    A filename or path, does not need to exist as a file
-     * @param int|string $options Either a PATHINFO_* constant,
-     *                            or a string name to return only the specified piece
-     *
-     * @return string|array
+     * @param  string  $dir
+     * @return bool
+     * @internal
      */
-    public static function pathinfo($path, $options = null)
+    protected function isWritablePath(string $dir): bool
     {
-        $ret = ['scheme' => '', 'dirname' => '', 'basename' => '', 'extension' => '', 'filename' => ''];
-        $pathinfo = [];
-        if (preg_match('#^((.*?)://)?(.*?)[\\\\/]*(([^/\\\\]*?)(\.([^\.\\\\/]+?)|))[\\\\/\.]*$#um', $path, $pathinfo)) {
-            if (array_key_exists(1, $pathinfo)) {
-                $ret['scheme'] = $pathinfo[2];
-                $ret['dirname'] = $pathinfo[1];
-            }
-            if (array_key_exists(3, $pathinfo)) {
-                $ret['dirname'] .= $pathinfo[3];
-            }
-            if (array_key_exists(4, $pathinfo)) {
-                $ret['basename'] = $pathinfo[4];
-            }
-            if (array_key_exists(7, $pathinfo)) {
-                $ret['extension'] = $pathinfo[7];
-            }
-            if (array_key_exists(5, $pathinfo)) {
-                $ret['filename'] = $pathinfo[5];
-            }
+        if ($dir === '') {
+            return false;
         }
-        switch ($options) {
-            case PATHINFO_DIRNAME:
-            case 'dirname':
-                return $ret['dirname'];
-            case PATHINFO_BASENAME:
-            case 'basename':
-                return $ret['basename'];
-            case PATHINFO_EXTENSION:
-            case 'extension':
-                return $ret['extension'];
-            case PATHINFO_FILENAME:
-            case 'filename':
-                return $ret['filename'];
-            default:
-                return $ret;
+
+        if (!file_exists($dir)) {
+            // Recursively look up in the directory tree.
+            return $this->isWritablePath($this->filesystem->parent($dir));
         }
+
+        return is_dir($dir) && is_writable($dir);
     }
 }
diff --git a/system/src/Grav/Framework/File/DataFile.php b/system/src/Grav/Framework/File/DataFile.php
index fd6b8957f..cd8fe1c89 100644
--- a/system/src/Grav/Framework/File/DataFile.php
+++ b/system/src/Grav/Framework/File/DataFile.php
@@ -34,7 +34,7 @@ class DataFile extends AbstractFile
     /**
      * (Re)Load a file and return RAW file contents.
      *
-     * @return array
+     * @return array|false
      * @throws RuntimeException
      */
     public function load()
@@ -42,7 +42,7 @@ class DataFile extends AbstractFile
         $raw = parent::load();
 
         try {
-            return $this->formatter->decode($raw);
+            return $raw !== false ? $this->formatter->decode($raw) : false;
         } catch (RuntimeException $e) {
             throw new RuntimeException(sprintf("Failed to load file '%s': %s", $this->getFilePath(), $e->getMessage()), $e->getCode(), $e);
         }
@@ -54,9 +54,10 @@ class DataFile extends AbstractFile
      * @param  string|array  $data  Data to be saved.
      * @throws RuntimeException
      */
-    public function save($data)
+    public function save($data): void
     {
         if (\is_string($data)) {
+            // Make sure that the string is valid data.
             try {
                 $this->formatter->decode($data);
             } catch (RuntimeException $e) {
diff --git a/system/src/Grav/Framework/File/File.php b/system/src/Grav/Framework/File/File.php
index bcac43941..31072b43c 100644
--- a/system/src/Grav/Framework/File/File.php
+++ b/system/src/Grav/Framework/File/File.php
@@ -16,11 +16,11 @@ class File extends AbstractFile
     /**
      * Load a file from the filesystem.
      *
-     * @return string
+     * @return string|false
      */
     public function load()
     {
-        return (string) parent::load();
+        return parent::load();
     }
 
     /**
@@ -29,8 +29,12 @@ class File extends AbstractFile
      * @param  string $data
      * @throws \RuntimeException
      */
-    public function save($data)
+    public function save($data): void
     {
+        if (!\is_string($data)) {
+            throw new \RuntimeException('Cannot save data, string required');
+        }
+
         parent::save($data);
     }
 }
diff --git a/system/src/Grav/Framework/File/Formatter/AbstractFormatter.php b/system/src/Grav/Framework/File/Formatter/AbstractFormatter.php
new file mode 100644
index 000000000..852f4e5b2
--- /dev/null
+++ b/system/src/Grav/Framework/File/Formatter/AbstractFormatter.php
@@ -0,0 +1,106 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @package    Grav\Framework\File\Formatter
+ *
+ * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
+ * @license    MIT License; see LICENSE file for details.
+ */
+
+namespace Grav\Framework\File\Formatter;
+
+abstract class AbstractFormatter implements FormatterInterface
+{
+    /** @var array */
+    private $config;
+
+    /**
+     * IniFormatter constructor.
+     * @param array $config
+     */
+    public function __construct(array $config = [])
+    {
+        $this->config = $config;
+    }
+
+    /**
+     * @return string
+     */
+    public function serialize(): string
+    {
+        return serialize($this->doSerialize());
+    }
+
+    /**
+     * @param string $serialized
+     */
+    public function unserialize($serialized): void
+    {
+        $this->doUnserialize(unserialize($serialized, false));
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getDefaultFileExtension(): string
+    {
+        $extensions = $this->getSupportedFileExtensions();
+
+        // Call fails on bad configuration.
+        return reset($extensions);
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    public function getSupportedFileExtensions(): array
+    {
+        // Call fails on bad configuration.
+        return $this->getConfig('file_extension');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    abstract public function encode($data): string;
+
+    /**
+     * {@inheritdoc}
+     */
+    abstract public function decode($data);
+
+    /**
+     * Get either full configuration or a single option.
+     *
+     * @param string|null $name Configuration option (optional)
+     * @return mixed
+     */
+    protected function getConfig(string $name = null)
+    {
+        if (null !== $name) {
+            return $this->config[$name] ?? null;
+        }
+
+        return $this->config;
+    }
+
+    /**
+     * @return array
+     */
+    protected function doSerialize(): array
+    {
+        return ['config' => $this->config];
+    }
+
+    /**
+     * Note: if overridden, make sure you call parent::doUnserialize()
+     *
+     * @param array $serialized
+     */
+    protected function doUnserialize(array $serialized): void
+    {
+        $this->config = $serialized['config'];
+    }
+}
diff --git a/system/src/Grav/Framework/File/Formatter/CsvFormatter.php b/system/src/Grav/Framework/File/Formatter/CsvFormatter.php
index 7bc89bbcc..6c4421ffa 100644
--- a/system/src/Grav/Framework/File/Formatter/CsvFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/CsvFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,50 +11,37 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class CsvFormatter implements FormatterInterface
+class CsvFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     /**
      * IniFormatter constructor.
      * @param array $config
      */
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
-                'file_extension' => ['.csv', '.tsv'],
-                'delimiter' => ','
-            ];
+        $config += [
+            'file_extension' => ['.csv', '.tsv'],
+            'delimiter' => ','
+        ];
+
+        parent::__construct($config);
+    }
+
+    /**
+     * Returns delimiter used to both encode and decode CSV.
+     *
+     * @return string
+     */
+    public function getDelimiter(): string
+    {
+        // Call fails on bad configuration.
+        return $this->getConfig('delimiter');
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getDefaultFileExtension()
-    {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    public function getDelimiter()
-    {
-        return $this->config['delimiter'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data, $delimiter = null)
+    public function encode($data, $delimiter = null): string
     {
         $delimiter = $delimiter ?? $this->getDelimiter();
         $header = array_keys(reset($lines));
@@ -71,7 +60,7 @@ class CsvFormatter implements FormatterInterface
     /**
      * {@inheritdoc}
      */
-    public function decode($data, $delimiter = null)
+    public function decode($data, $delimiter = null): array
     {
         $delimiter = $delimiter ?? $this->getDelimiter();
         $lines = preg_split('/\r\n|\r|\n/', $data);
diff --git a/system/src/Grav/Framework/File/Formatter/FormatterInterface.php b/system/src/Grav/Framework/File/Formatter/FormatterInterface.php
index 1149eb23e..04793461a 100644
--- a/system/src/Grav/Framework/File/Formatter/FormatterInterface.php
+++ b/system/src/Grav/Framework/File/Formatter/FormatterInterface.php
@@ -1,7 +1,9 @@
 <?php
 
+declare(strict_types=1);
+
 /**
- * @package    Grav\Framework\File\Formatter
+ * @package    Grav\Framework\File
  *
  * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
  * @license    MIT License; see LICENSE file for details.
@@ -9,7 +11,7 @@
 
 namespace Grav\Framework\File\Formatter;
 
-interface FormatterInterface
+interface FormatterInterface extends \Serializable
 {
     /**
      * Get default file extension from current formatter (with dot).
@@ -18,14 +20,14 @@ interface FormatterInterface
      *
      * @return string File extension (can be empty).
      */
-    public function getDefaultFileExtension();
+    public function getDefaultFileExtension(): string;
 
     /**
      * Get file extensions supported by current formatter (with dot).
      *
      * @return string[]
      */
-    public function getSupportedFileExtensions();
+    public function getSupportedFileExtensions(): array;
 
     /**
      * Encode data into a string.
@@ -33,13 +35,13 @@ interface FormatterInterface
      * @param array $data
      * @return string
      */
-    public function encode($data);
+    public function encode($data): string;
 
     /**
      * Decode a string into data.
      *
      * @param string $data
-     * @return array
+     * @return mixed
      */
     public function decode($data);
-}
\ No newline at end of file
+}
diff --git a/system/src/Grav/Framework/File/Formatter/IniFormatter.php b/system/src/Grav/Framework/File/Formatter/IniFormatter.php
index 754edf5f8..e81f599ef 100644
--- a/system/src/Grav/Framework/File/Formatter/IniFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/IniFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,44 +11,25 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class IniFormatter implements FormatterInterface
+class IniFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     /**
      * IniFormatter constructor.
      * @param array $config
      */
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
-                'file_extension' => '.ini'
-            ];
+        $config += [
+            'file_extension' => '.ini'
+        ];
+
+        parent::__construct($config);
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getDefaultFileExtension()
-    {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data)
+    public function encode($data): string
     {
         $string = '';
         foreach ($data as $key => $value) {
@@ -63,7 +46,7 @@ class IniFormatter implements FormatterInterface
     /**
      * {@inheritdoc}
      */
-    public function decode($data)
+    public function decode($data): array
     {
         $decoded = @parse_ini_string($data);
 
diff --git a/system/src/Grav/Framework/File/Formatter/JsonFormatter.php b/system/src/Grav/Framework/File/Formatter/JsonFormatter.php
index 3ff3adfe7..7e1ac8e8d 100644
--- a/system/src/Grav/Framework/File/Formatter/JsonFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/JsonFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,47 +11,70 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class JsonFormatter implements FormatterInterface
+class JsonFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
+        $config += [
             'file_extension' => '.json',
             'encode_options' => 0,
-            'decode_assoc' => true
+            'decode_assoc' => true,
+            'decode_depth' => 512,
+            'decode_options' => 0
         ];
+
+        parent::__construct($config);
+    }
+
+    /**
+     * Returns options used in encode() function.
+     *
+     * @return int
+     */
+    public function getEncodeOptions(): int
+    {
+        return $this->getConfig('encode_options');
+    }
+
+    /**
+     * Returns options used in decode() function.
+     *
+     * @return int
+     */
+    public function getDecodeOptions(): int
+    {
+        return $this->getConfig('decode_options');
+    }
+
+    /**
+     * Returns recursion depth used in decode() function.
+     *
+     * @return int
+     */
+    public function getDecodeDepth(): int
+    {
+        return $this->getConfig('decode_depth');
+    }
+
+    /**
+     * Returns true if JSON objects will be converted into associative arrays.
+     *
+     * @return bool
+     */
+    public function getDecodeAssoc(): bool
+    {
+        return $this->getConfig('decode_assoc');
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getDefaultFileExtension()
+    public function encode($data): string
     {
-        $extensions = $this->getSupportedFileExtensions();
+        $encoded = @json_encode($data, $this->getEncodeOptions());
 
-        return (string) reset($extensions);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data)
-    {
-        $encoded = @json_encode($data, $this->config['encode_options']);
-
-        if ($encoded === false) {
-            throw new \RuntimeException('Encoding JSON failed');
+        if ($encoded === false && json_last_error() !== JSON_ERROR_NONE) {
+            throw new \RuntimeException('Encoding JSON failed: ' . json_last_error_msg());
         }
 
         return $encoded;
@@ -60,10 +85,10 @@ class JsonFormatter implements FormatterInterface
      */
     public function decode($data)
     {
-        $decoded = @json_decode($data, $this->config['decode_assoc']);
+        $decoded = @json_decode($data, $this->getDecodeAssoc(), $this->getDecodeDepth(), $this->getDecodeOptions());
 
-        if ($decoded === false) {
-            throw new \RuntimeException('Decoding JSON failed');
+        if (null === $decoded && json_last_error() !== JSON_ERROR_NONE) {
+            throw new \RuntimeException('Decoding JSON failed: ' . json_last_error_msg());
         }
 
         return $decoded;
diff --git a/system/src/Grav/Framework/File/Formatter/MarkdownFormatter.php b/system/src/Grav/Framework/File/Formatter/MarkdownFormatter.php
index 181e4477e..348c84890 100644
--- a/system/src/Grav/Framework/File/Formatter/MarkdownFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/MarkdownFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,16 +11,16 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class MarkdownFormatter implements FormatterInterface
+use Grav\Framework\File\Interfaces\FileFormatterInterface;
+
+class MarkdownFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
     /** @var FormatterInterface */
     private $headerFormatter;
 
-    public function __construct(array $config = [], FormatterInterface $headerFormatter = null)
+    public function __construct(array $config = [], FileFormatterInterface $headerFormatter = null)
     {
-        $this->config = $config + [
+        $config += [
             'file_extension' => '.md',
             'header' => 'header',
             'body' => 'markdown',
@@ -26,34 +28,58 @@ class MarkdownFormatter implements FormatterInterface
             'yaml' => ['inline' => 20]
         ];
 
-        $this->headerFormatter = $headerFormatter ?: new YamlFormatter($this->config['yaml']);
+        parent::__construct($config);
+
+        $this->headerFormatter = $headerFormatter ?: new YamlFormatter($config['yaml']);
+    }
+
+    /**
+     * Returns header field used in both encode() and decode().
+     *
+     * @return string
+     */
+    public function getHeaderField(): string
+    {
+        return $this->getConfig('header');
+    }
+
+    /**
+     * Returns body field used in both encode() and decode().
+     *
+     * @return string
+     */
+    public function getBodyField(): string
+    {
+        return $this->getConfig('body');
+    }
+
+    /**
+     * Returns raw field used in both encode() and decode().
+     *
+     * @return string
+     */
+    public function getRawField(): string
+    {
+        return $this->getConfig('raw');
+    }
+
+    /**
+     * Returns header formatter object used in both encode() and decode().
+     *
+     * @return FileFormatterInterface
+     */
+    public function getHeaderFormatter(): FileFormatterInterface
+    {
+        return $this->headerFormatter;
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getDefaultFileExtension()
+    public function encode($data): string
     {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data)
-    {
-        $headerVar = $this->config['header'];
-        $bodyVar = $this->config['body'];
+        $headerVar = $this->getHeaderField();
+        $bodyVar = $this->getBodyField();
 
         $header = isset($data[$headerVar]) ? (array) $data[$headerVar] : [];
         $body = isset($data[$bodyVar]) ? (string) $data[$bodyVar] : '';
@@ -61,7 +87,7 @@ class MarkdownFormatter implements FormatterInterface
         // Create Markdown file with YAML header.
         $encoded = '';
         if ($header) {
-            $encoded = "---\n" . trim($this->headerFormatter->encode($data['header'])) . "\n---\n\n";
+            $encoded = "---\n" . trim($this->getHeaderFormatter()->encode($data['header'])) . "\n---\n\n";
         }
         $encoded .= $body;
 
@@ -74,12 +100,13 @@ class MarkdownFormatter implements FormatterInterface
     /**
      * {@inheritdoc}
      */
-    public function decode($data)
+    public function decode($data): array
     {
-        $headerVar = $this->config['header'];
-        $bodyVar = $this->config['body'];
-        $rawVar = $this->config['raw'];
+        $headerVar = $this->getHeaderField();
+        $bodyVar = $this->getBodyField();
+        $rawVar = $this->getRawField();
 
+        // Define empty content
         $content = [
             $headerVar => [],
             $bodyVar => ''
@@ -100,7 +127,7 @@ class MarkdownFormatter implements FormatterInterface
             if ($rawVar) {
                 $content[$rawVar] = $frontmatter;
             }
-            $content[$headerVar] = $this->headerFormatter->decode($frontmatter);
+            $content[$headerVar] = $this->getHeaderFormatter()->decode($frontmatter);
             $content[$bodyVar] = $matches[2];
         }
 
diff --git a/system/src/Grav/Framework/File/Formatter/SerializeFormatter.php b/system/src/Grav/Framework/File/Formatter/SerializeFormatter.php
index 4e9ef9773..d1c4fa970 100644
--- a/system/src/Grav/Framework/File/Formatter/SerializeFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/SerializeFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -9,44 +11,38 @@
 
 namespace Grav\Framework\File\Formatter;
 
-class SerializeFormatter implements FormatterInterface
+class SerializeFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     /**
      * IniFormatter constructor.
      * @param array $config
      */
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
-                'file_extension' => '.ser'
-            ];
+        $config += [
+            'file_extension' => '.ser',
+            'decode_options' => ['allowed_classes' => [\stdClass::class]]
+        ];
+
+        parent::__construct($config);
     }
 
     /**
-     * {@inheritdoc}
+     * Returns options used in decode().
+     *
+     * By default only allow stdClass class.
+     *
+     * @return array|bool
      */
-    public function getDefaultFileExtension()
+    public function getOptions()
     {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
+        return $this->getConfig('decode_options');
     }
 
     /**
      * {@inheritdoc}
      */
-    public function getSupportedFileExtensions()
-    {
-        return (array) $this->config['file_extension'];
-    }
-
-    /**
-     * {@inheritdoc}
-     */
-    public function encode($data)
+    public function encode($data): string
     {
         return serialize($this->preserveLines($data, ["\n", "\r"], ['\\n', '\\r']));
     }
@@ -56,9 +52,9 @@ class SerializeFormatter implements FormatterInterface
      */
     public function decode($data)
     {
-        $decoded = @unserialize($data);
+        $decoded = @unserialize($data, $this->getOptions());
 
-        if ($decoded === false) {
+        if ($decoded === false && $data !== serialize(false)) {
             throw new \RuntimeException('Decoding serialized data failed');
         }
 
@@ -73,7 +69,7 @@ class SerializeFormatter implements FormatterInterface
      * @param array $replace
      * @return mixed
      */
-    protected function preserveLines($data, $search, $replace)
+    protected function preserveLines($data, array $search, array $replace)
     {
         if (\is_string($data)) {
             $data = str_replace($search, $replace, $data);
diff --git a/system/src/Grav/Framework/File/Formatter/YamlFormatter.php b/system/src/Grav/Framework/File/Formatter/YamlFormatter.php
index 0a2ea04c1..78fde2b4a 100644
--- a/system/src/Grav/Framework/File/Formatter/YamlFormatter.php
+++ b/system/src/Grav/Framework/File/Formatter/YamlFormatter.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 /**
  * @package    Grav\Framework\File\Formatter
  *
@@ -14,50 +16,63 @@ use Symfony\Component\Yaml\Exception\ParseException;
 use Symfony\Component\Yaml\Yaml as YamlParser;
 use RocketTheme\Toolbox\Compat\Yaml\Yaml as FallbackYamlParser;
 
-class YamlFormatter implements FormatterInterface
+class YamlFormatter extends AbstractFormatter
 {
-    /** @var array */
-    private $config;
-
     public function __construct(array $config = [])
     {
-        $this->config = $config + [
+        $config += [
             'file_extension' => '.yaml',
             'inline' => 5,
             'indent' => 2,
             'native' => true,
             'compat' => true
         ];
+
+        parent::__construct($config);
     }
 
     /**
-     * {@inheritdoc}
+     * @return int
      */
-    public function getDefaultFileExtension()
+    public function getInlineOption(): int
     {
-        $extensions = $this->getSupportedFileExtensions();
-
-        return (string) reset($extensions);
+        return $this->getConfig('inline');
     }
 
     /**
-     * {@inheritdoc}
+     * @return int
      */
-    public function getSupportedFileExtensions()
+    public function getIndentOption(): int
     {
-        return (array) $this->config['file_extension'];
+        return $this->getConfig('indent');
+    }
+
+    /**
+     * @return bool
+     */
+    public function useNativeDecoder(): bool
+    {
+        return $this->getConfig('native');
+    }
+
+    /**
+     * @return bool
+     */
+    public function useCompatibleDecoder(): bool
+    {
+        return $this->getConfig('compat');
     }
 
     /**
      * {@inheritdoc}
      */
-    public function encode($data, $inline = null, $indent = null)
+    public function encode($data, $inline = null, $indent = null): string
     {
         try {
-            return (string) YamlParser::dump(
+            return YamlParser::dump(
                 $data,
-                $inline ? (int) $inline : $this->config['inline'],
-                $indent ? (int) $indent : $this->config['indent'],
+                $inline ? (int) $inline : $this->getInlineOption(),
+                $indent ? (int) $indent : $this->getIndentOption(),
                 YamlParser::DUMP_EXCEPTION_ON_INVALID_TYPE
             );
         } catch (DumpException $e) {
@@ -68,10 +83,10 @@ class YamlFormatter implements FormatterInterface
     /**
      * {@inheritdoc}
      */
-    public function decode($data)
+    public function decode($data): array
     {
         // Try native PECL YAML PHP extension first if available.
-        if (\function_exists('yaml_parse') && $this->config['native']) {
+        if (\function_exists('yaml_parse') && $this->useNativeDecoder()) {
             // Safely decode YAML.
             $saved = @ini_get('yaml.decode_php');
             @ini_set('yaml.decode_php', 0);
@@ -79,14 +94,14 @@ class YamlFormatter implements FormatterInterface
             @ini_set('yaml.decode_php', $saved);
 
             if ($decoded !== false) {
-                return (array) $decoded;
+                return $decoded;
             }
         }
 
         try {
-            return (array) YamlParser::parse($data);
+            return YamlParser::parse($data);
         } catch (ParseException $e) {
-            if ($this->config['compat']) {
+            if ($this->useCompatibleDecoder()) {
                 return (array) FallbackYamlParser::parse($data);
             }
 
diff --git a/system/src/Grav/Framework/File/Interfaces/FileInterface.php b/system/src/Grav/Framework/File/Interfaces/FileInterface.php
index 3aa8745ea..9c727398b 100644
--- a/system/src/Grav/Framework/File/Interfaces/FileInterface.php
+++ b/system/src/Grav/Framework/File/Interfaces/FileInterface.php
@@ -11,64 +11,64 @@ declare(strict_types=1);
 
 namespace Grav\Framework\File\Interfaces;
 
-interface FileInterface
+interface FileInterface extends \Serializable
 {
     /**
      * Get full path to the file.
      *
      * @return string
      */
-    public function getFilePath() : string;
+    public function getFilePath(): string;
 
     /**
      * Get path to the file.
      *
      * @return string
      */
-    public function getPath() : string;
+    public function getPath(): string;
 
     /**
      * Get filename.
      *
      * @return string
      */
-    public function getFilename() : string;
+    public function getFilename(): string;
 
     /**
      * Return name of the file without extension.
      *
      * @return string
      */
-    public function getBasename() : string;
+    public function getBasename(): string;
 
     /**
      * Return file extension.
      *
-     * @param $withDot
+     * @param bool $withDot
      * @return string
      */
-    public function getExtension($withDot = false) : string;
+    public function getExtension(bool $withDot = false): string;
 
     /**
      * Check if file exits.
      *
      * @return bool
      */
-    public function exists() : bool;
+    public function exists(): bool;
 
     /**
      * Return file modification time.
      *
-     * @return int|bool Timestamp or false if file doesn't exist.
+     * @return int Unix timestamp. If file does not exist, method returns current time.
      */
-    public function getCreationTime();
+    public function getCreationTime(): int;
 
     /**
      * Return file modification time.
      *
-     * @return int|bool Timestamp or false if file doesn't exist.
+     * @return int Unix timestamp. If file does not exist, method returns current time.
      */
-    public function getModificationTime();
+    public function getModificationTime(): int;
 
     /**
      * Lock file for writing. You need to manually unlock().
@@ -77,33 +77,40 @@ interface FileInterface
      * @return bool
      * @throws \RuntimeException
      */
-    public function lock($block = true) : bool;
+    public function lock(bool $block = true): bool;
 
     /**
      * Unlock file.
      *
      * @return bool
      */
-    public function unlock() : bool;
+    public function unlock(): bool;
 
     /**
      * Returns true if file has been locked for writing.
      *
      * @return bool True = locked, false = not locked.
      */
-    public function isLocked() : bool;
+    public function isLocked(): bool;
+
+    /**
+     * Check if file exists and can be read.
+     *
+     * @return bool
+     */
+    public function isReadable(): bool;
 
     /**
      * Check if file can be written.
      *
      * @return bool
      */
-    public function isWritable() : bool;
+    public function isWritable(): bool;
 
     /**
      * (Re)Load a file and return RAW file contents.
      *
-     * @return string
+     * @return string|array|false
      */
     public function load();
 
@@ -113,7 +120,7 @@ interface FileInterface
      * @param  mixed $data
      * @throws \RuntimeException
      */
-    public function save($data);
+    public function save($data): void;
 
     /**
      * Rename file in the filesystem if it exists.
@@ -121,26 +128,12 @@ interface FileInterface
      * @param string $path
      * @return bool
      */
-    public function rename($path) : bool;
+    public function rename(string $path): bool;
 
     /**
      * Delete file from filesystem.
      *
      * @return bool
      */
-    public function delete() : bool;
-
-    /**
-     * Multi-byte-safe pathinfo replacement.
-     * Replacement for pathinfo(), but stream, multibyte and cross-platform safe.
-     *
-     * @see    http://www.php.net/manual/en/function.pathinfo.php
-     *
-     * @param string     $path    A filename or path, does not need to exist as a file
-     * @param int|string $options Either a PATHINFO_* constant,
-     *                            or a string name to return only the specified piece
-     *
-     * @return string|array
-     */
-    public static function pathinfo($path, $options = null);
+    public function delete(): bool;
 }
diff --git a/system/src/Grav/Framework/Filesystem/Filesystem.php b/system/src/Grav/Framework/Filesystem/Filesystem.php
new file mode 100644
index 000000000..01a1cece3
--- /dev/null
+++ b/system/src/Grav/Framework/Filesystem/Filesystem.php
@@ -0,0 +1,268 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * @package    Grav\Framework\Filesystem
+ *
+ * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
+ * @license    MIT License; see LICENSE file for details.
+ */
+
+namespace Grav\Framework\Filesystem;
+
+class Filesystem
+{
+    /** @var bool|null */
+    private $normalizeNext;
+
+    /**
+     * Force paths to be normalized in the next call.
+     *
+     * Note: Normalizing option will be reset after the next method call.
+     *
+     * @return $this
+     */
+    public function unsafe()
+    {
+        $this->normalizeNext = true;
+
+        return $this;
+    }
+
+    /**
+     * Tell that all the paths are save to be used (already normalized) in the next call.
+     *
+     * Note: Normalizing option will be reset after the next method call.
+     *
+     * @return $this
+     */
+    public function safe()
+    {
+        $this->normalizeNext = false;
+
+        return $this;
+    }
+
+    /**
+     * Returns parent path. Empty path is returned if there are no segments remaining.
+     *
+     * Can be used recursively to get towards the root directory.
+     *
+     * @param string $path
+     * @param int $levels
+     * @return string
+     * @throws \RuntimeException
+     */
+    public function parent(string $path, int $levels = 1): string
+    {
+        [$scheme, $path] = $this->getSchemeAndHierarchy($path);
+
+        if ($this->normalizeNext !== false) {
+            $path = $this->normalizePathPart($path);
+        }
+        $this->normalizeNext = null;
+
+        if ($path === '') {
+            return '';
+        }
+
+        [$scheme, $parent] = $this->dirnameInternal($scheme, $path, $levels);
+
+        return $parent !== $path ? $this->toString($scheme, $parent) : '';
+    }
+
+    /**
+     * Normalize path by cleaning up \ , /./ , // and /../
+     *
+     * @param string $path
+     * @return string
+     * @throws \RuntimeException
+     */
+    public function normalize(string $path): string
+    {
+        if ($this->normalizeNext === false) {
+            $this->normalizeNext = null;
+
+            return $path;
+        }
+
+        [$scheme, $path] = $this->getSchemeAndHierarchy($path);
+
+        $path = $this->normalizePathPart($path);
+
+        return $this->toString($scheme, $path);
+    }
+
+    /**
+     * Stream safe dirname() replacement.
+     *
+     * @see   http://php.net/manual/en/function.dirname.php
+     *
+     * @param string $path
+     * @param int $levels
+     * @return string
+     * @throws \RuntimeException
+     */
+    public function dirname(string $path, int $levels = 1): string
+    {
+        [$scheme, $path] = $this->getSchemeAndHierarchy($path);
+
+        if ($this->normalizeNext || ($scheme && null === $this->normalizeNext)) {
+            $path = $this->normalizePathPart($path);
+        }
+        $this->normalizeNext = null;
+
+        [$scheme, $path] = $this->dirnameInternal($scheme, $path, $levels);
+
+        return $this->toString($scheme, $path);
+    }
+
+    /**
+     * Multi-byte and stream-safe pathinfo() replacement.
+     *
+     * Replacement for pathinfo(), but stream, multibyte and cross-platform safe.
+     *
+     * @see   http://www.php.net/manual/en/function.pathinfo.php
+     *
+     * @param string     $path     A filename or path, does not need to exist as a file
+     * @param int|string $options Either a PATHINFO_* constant, or a string name to return only the specified piece
+     *
+     * @return array|string
+     */
+    public function pathinfo(string $path, int $options = null)
+    {
+        [$scheme, $path] = $this->getSchemeAndHierarchy($path);
+
+        if ($this->normalizeNext || ($scheme && null === $this->normalizeNext)) {
+            $path = $this->normalizePathPart($path);
+        }
+        $this->normalizeNext = null;
+
+        return $this->pathinfoInternal($scheme, $path, $options);
+    }
+
+    /**
+     * @param string|null $scheme
+     * @param string $path
+     * @param int $levels
+     * @return array
+     */
+    protected function dirnameInternal(?string $scheme, string $path, int $levels = 1): array
+    {
+        $path = \dirname($path, $levels);
+
+        if (null !== $scheme && $path === '.') {
+            return [$scheme, ''];
+        }
+
+        return [$scheme, $path];
+    }
+
+    /**
+     * @param string|null $scheme
+     * @param string $path
+     * @param int|null $options
+     */
+    protected function pathinfoInternal(?string $scheme, string $path, int $options = null)
+    {
+        $info = $options ? \pathinfo($path, $options) : \pathinfo($path);
+
+        if (null !== $scheme) {
+            $info['scheme'] = $scheme;
+            $dirname = isset($info['dirname']) && $info['dirname'] !== '.' ? $info['dirname'] : null;
+
+            if (null !== $dirname) {
+                $info['dirname'] = $scheme . '://' . $dirname;
+            } else {
+                $info = ['dirname' => $scheme . '://'] + $info;
+            }
+        }
+
+        return $info;
+    }
+
+    /**
+     * Gets a 2-tuple of scheme (may be null) and hierarchical part of a filename (e.g. file:///tmp -> array(file, tmp)).
+     *
+     * @param string $filename
+     * @return array
+     */
+    protected function getSchemeAndHierarchy(string $filename): array
+    {
+        $components = explode('://', $filename, 2);
+
+        return 2 === \count($components) ? $components : [null, $components[0]];
+    }
+
+    /**
+     * @param string|null $scheme
+     * @param string $path
+     * @return string
+     */
+    protected function toString(?string $scheme, string $path): string
+    {
+        if ($scheme) {
+            return $scheme . '://' . $path;
+        }
+
+        return $path;
+    }
+
+    /**
+     * @param string $path
+     * @return string
+     * @throws \RuntimeException
+     */
+    protected function normalizePathPart(string $path): string
+    {
+        // Quick check for empty path.
+        if ($path === '' || $path === '.') {
+            return '';
+        }
+
+        // Quick check for root.
+        if ($path === '/') {
+            return '/';
+        }
+
+        // If the last character is not '/' or any of '\', './', '//' and '..' are not found, path is clean and we're done.
+        if ($path[-1] !== '/' && !preg_match('`(\\\\|\./|//|\.\.)`', $path)) {
+            return $path;
+        }
+
+        // Convert backslashes
+        $path = strtr($path, ['\\' => '/']);
+
+        $parts = explode('/', $path);
+
+        // Keep absolute paths.
+        $root = '';
+        if ($parts[0] === '') {
+            $root = '/';
+            array_shift($parts);
+        }
+
+        $list = [];
+        foreach ($parts as $i => $part) {
+            // Remove empty parts: // and /./
+            if ($part === '' || $part === '.') {
+                continue;
+            }
+
+            // Resolve /../ by removing path part.
+            if ($part === '..') {
+                $test = array_shift($list);
+                if ($test === null) {
+                    // Oops, user tried to access something outside of our root folder.
+                    throw new \RuntimeException("Bad path {$path}");
+                }
+            }
+
+            $list[] = $part;
+        }
+
+        // Build path back together.
+        return $root . implode('/', $list);
+    }
+}
diff --git a/system/src/Grav/Framework/Flex/FlexForm.php b/system/src/Grav/Framework/Flex/FlexForm.php
index 193d87a4a..ab3a84c07 100644
--- a/system/src/Grav/Framework/Flex/FlexForm.php
+++ b/system/src/Grav/Framework/Flex/FlexForm.php
@@ -16,6 +16,7 @@ use Grav\Common\Grav;
 use Grav\Common\Utils;
 use Grav\Framework\Flex\Interfaces\FlexFormInterface;
 use Grav\Framework\Flex\Interfaces\FlexObjectInterface;
+use Grav\Framework\Form\FormFlash;
 use Grav\Framework\Route\Route;
 use Psr\Http\Message\ServerRequestInterface;
 use Psr\Http\Message\UploadedFileInterface;
@@ -36,31 +37,33 @@ class FlexForm implements FlexFormInterface
     private $submitted;
     /** @var string[] */
     private $errors;
-    /** @var Data */
+    /** @var Data|FlexObjectInterface */
     private $data;
-    /** @var UploadedFileInterface[] */
+    /** @var array|UploadedFileInterface[] */
     private $files;
     /** @var FlexObjectInterface */
     private $object;
+    /** @var FormFlash */
+    private $flash;
 
     /**
      * FlexForm constructor.
      * @param string $name
-     * @param FlexObjectInterface|null $object
+     * @param FlexObjectInterface $object
      */
-    public function __construct(string $name = '', FlexObjectInterface $object = null)
+    public function __construct(string $name, FlexObjectInterface $object)
     {
-        $this->reset();
-
-        if ($object) {
-            $this->setObject($object);
-        }
-
         $this->name = $name;
-        $this->id = $this->getName();
+        $this->setObject($object);
+        $this->setId($this->getName());
+        $this->reset();
     }
 
     /**
+     * Get HTML id="..." attribute.
+     *
+     * Defaults to 'flex-[type]-[name]', where 'type' is object type and 'name' is the first parameter given in constructor.
+     *
      * @return string
      */
     public function getId(): string
@@ -69,6 +72,8 @@ class FlexForm implements FlexFormInterface
     }
 
     /**
+     * Sets HTML id="" attribute.
+     *
      * @param string $id
      */
     public function setId(string $id): void
@@ -77,34 +82,10 @@ class FlexForm implements FlexFormInterface
     }
 
     /**
-     * @return string
-     */
-    public function getName(): string
-    {
-        $object = $this->object;
-        $name = $this->name ?: 'object';
-
-        return "flex-{$object->getType(false)}-{$name}";
-    }
-
-
-    /**
-     * @return string
-     */
-    public function getNonceName(): string
-    {
-        return 'nonce';
-    }
-
-    /**
-     * @return string
-     */
-    public function getNonceAction(): string
-    {
-        return 'flex-object';
-    }
-
-    /**
+     * Get unique id for the current form instance. By default regenerated on every page reload.
+     *
+     * This id is used to load the saved form state, if available.
+     *
      * @return string
      */
     public function getUniqueId(): string
@@ -116,6 +97,51 @@ class FlexForm implements FlexFormInterface
         return $this->uniqueid;
     }
 
+    /**
+     * Sets unique form id allowing you to attach the form state to the object for example.
+     *
+     * @param string $uniqueId
+     */
+    public function setUniqueId(string $uniqueId): void
+    {
+        $this->uniqueid = $uniqueId;
+    }
+
+    /**
+     * @return string
+     */
+    public function getName(): string
+    {
+        $object = $this->getObject();
+        $name = $this->name ?: 'object';
+
+        return "flex-{$object->getType(false)}-{$name}";
+    }
+
+    /**
+     * @return string
+     */
+    public function getFormName(): string
+    {
+        return $this->name;
+    }
+
+    /**
+     * @return string
+     */
+    public function getNonceName(): string
+    {
+        return 'form-nonce';
+    }
+
+    /**
+     * @return string
+     */
+    public function getNonceAction(): string
+    {
+        return 'form';
+    }
+
     /**
      * @return string
      */
@@ -125,29 +151,20 @@ class FlexForm implements FlexFormInterface
         return '';
     }
 
-    /**
-     * @return array
-     */
-    public function getButtons(): array
-    {
-        return [
-            [
-                'type' => 'submit',
-                'value' => 'Save'
-            ]
-        ];
-    }
-
     /**
      * @return Data|FlexObjectInterface
      */
     public function getData()
     {
-        if (null === $this->data) {
-            $this->data = $this->getObject();
-        }
+        return $this->data ?? $this->getObject();
+    }
 
-        return $this->data;
+    /**
+     * @return array|UploadedFileInterface[]
+     */
+    public function getFiles(): array
+    {
+        return $this->files;
     }
 
     /**
@@ -160,57 +177,11 @@ class FlexForm implements FlexFormInterface
      */
     public function getValue(string $name)
     {
-        $data = $this->getData();
-        return $data instanceof FlexObject ? $data->getNestedProperty($name) : $data->get($name);
-    }
-
-    /**
-     * @return UploadedFileInterface[]
-     */
-    public function getFiles(): array
-    {
-        return $this->files;
-    }
-
-    /**
-     * @return Route|null
-     */
-    public function getFileUploadAjaxRoute(): ?Route
-    {
-        $object = $this->getObject();
-        if (!method_exists($object, 'route')) {
-            return null;
+        if (null === $this->data) {
+            return $this->getObject()->getNestedProperty($name);
         }
 
-        return $object->route('/edit.json/task:media.upload');
-    }
-
-    /**
-     * @param $field
-     * @param $filename
-     * @return Route|null
-     */
-    public function getFileDeleteAjaxRoute($field, $filename): ?Route
-    {
-        $object = $this->getObject();
-        if (!method_exists($object, 'route')) {
-            return null;
-        }
-
-        return $object->route('/edit.json/task:media.delete');
-    }
-
-    /**
-     * Note: this method clones the object.
-     *
-     * @param FlexObjectInterface $object
-     * @return $this
-     */
-    public function setObject(FlexObjectInterface $object): FlexFormInterface
-    {
-        $this->object = clone $object;
-
-        return $this;
+        return $this->data->get($name);
     }
 
     /**
@@ -218,10 +189,6 @@ class FlexForm implements FlexFormInterface
      */
     public function getObject(): FlexObjectInterface
     {
-        if (!$this->object) {
-            throw new \RuntimeException('FlexForm: Object is not defined');
-        }
-
         return $this->object;
     }
 
@@ -285,26 +252,14 @@ class FlexForm implements FlexFormInterface
             }
 
             $this->files = $files ?? [];
-            $this->data = new Data($this->decodeData($data['data'] ?? []));
+            $this->data = new Data($this->decodeData($data['data'] ?? []), $this->getBlueprint());
             if ($this->getErrors()) {
                 return $this;
             }
 
-            $this->validate();
+            $this->doSubmit($this->data->toArray(), $this->files);
 
             $this->submitted = true;
-
-            $object = clone $this->object;
-            $object->update($this->data->toArray());
-            $object->triggerEvent('onSave');
-
-            if (method_exists($object, 'upload')) {
-                $object->upload($this->files);
-            }
-            $object->save();
-
-            $this->object = $object;
-            $this->valid = true;
         } catch (ValidationException $e) {
             $list = [];
             foreach ($e->getMessages() as $field => $errors) {
@@ -386,6 +341,33 @@ class FlexForm implements FlexFormInterface
         $this->object = $data['object'];
     }
 
+    /**
+     * @return Route|null
+     */
+    public function getFileUploadAjaxRoute(): ?Route
+    {
+        $object = $this->getObject();
+        if (!method_exists($object, 'route')) {
+            return null;
+        }
+
+        return $object->route('/edit.json/task:media.upload');
+    }
+
+    /**
+     * @param $field
+     * @param $filename
+     * @return Route|null
+     */
+    public function getFileDeleteAjaxRoute($field, $filename): ?Route
+    {
+        $object = $this->getObject();
+        if (!method_exists($object, 'route')) {
+            return null;
+        }
+
+        return $object->route('/edit.json/task:media.delete');
+    }
 
     public function getMediaTaskRoute(): string
     {
@@ -405,6 +387,33 @@ class FlexForm implements FlexFormInterface
         return '/' . $this->object->getKey();
     }
 
+    /**
+     * Note: this method clones the object.
+     *
+     * @param FlexObjectInterface $object
+     * @return $this
+     */
+    protected function setObject(FlexObjectInterface $object): FlexFormInterface
+    {
+        $this->object = clone $object;
+
+        return $this;
+    }
+
+    /**
+     * Get flash object
+     *
+     * @return FormFlash
+     */
+    protected function getFlash()
+    {
+        if (null === $this->flash) {
+            $this->flash = new FormFlash($this->getName(), $this->getUniqueId());
+        }
+
+        return $this->flash;
+    }
+
     /**
      * @throws \Exception
      */
@@ -415,6 +424,41 @@ class FlexForm implements FlexFormInterface
         $this->checkUploads($this->files);
     }
 
+    protected function setErrors(array $errors): void
+    {
+        $this->errors = array_merge($this->errors, $errors);
+    }
+
+    protected function setError(string $error): void
+    {
+        $this->errors[] = $error;
+    }
+
+    /**
+     * @param array $data
+     * @param array $files
+     * @throws \Exception
+     */
+    protected function doSubmit(array $data, array $files)
+    {
+        $this->validate();
+
+        $object = clone $this->object;
+        $object->update($data);
+
+        if (method_exists($object, 'triggerEvent')) {
+            $object->triggerEvent('onSave');
+        }
+
+        if (method_exists($object, 'upload')) {
+            $object->upload($files);
+        }
+
+        $object->save();
+
+        $this->object = $object;
+    }
+
     protected function checkUploads(array $files): void
     {
         foreach ($files as $file) {
diff --git a/system/src/Grav/Framework/Flex/FlexObject.php b/system/src/Grav/Framework/Flex/FlexObject.php
index e5cc56018..af38f40c0 100644
--- a/system/src/Grav/Framework/Flex/FlexObject.php
+++ b/system/src/Grav/Framework/Flex/FlexObject.php
@@ -18,6 +18,7 @@ use Grav\Common\Page\Medium\MediumFactory;
 use Grav\Common\Twig\Twig;
 use Grav\Framework\ContentBlock\HtmlBlock;
 use Grav\Framework\Flex\Interfaces\FlexAuthorizeInterface;
+use Grav\Framework\Flex\Interfaces\FlexFormInterface;
 use Grav\Framework\Flex\Traits\FlexAuthorizeTrait;
 use Grav\Framework\Object\Access\NestedArrayAccessTrait;
 use Grav\Framework\Object\Access\NestedPropertyTrait;
@@ -170,7 +171,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
     public function getForm(string $name = '')
     {
         if (!isset($this->_forms[$name])) {
-            $this->_forms[$name] = new FlexForm($name, $this);
+            $this->_forms[$name] = $this->createFormObject($name);
         }
 
         return $this->_forms[$name];
@@ -662,4 +663,15 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
 
         unset ($elements['storage_key'], $elements['storage_timestamp']);
     }
+
+    /**
+     * This methods allows you to override form objects in child classes.
+     *
+     * @param string $name Form name
+     * @return FlexFormInterface
+     */
+    protected function createFormObject(string $name): FlexFormInterface
+    {
+        return new FlexForm($name, $this);
+    }
 }
diff --git a/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php b/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php
index 1a6bc7e46..dedf059dc 100644
--- a/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php
+++ b/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php
@@ -31,6 +31,16 @@ interface FlexFormInterface extends \Serializable
      */
     public function setId(string $id): void;
 
+    /**
+     * @return string
+     */
+    public function getUniqueId(): string;
+
+    /**
+     * @param string $uniqueId
+     */
+    public function setUniqueId(string $uniqueId): void;
+
     /**
      * @return string
      */
@@ -47,21 +57,11 @@ interface FlexFormInterface extends \Serializable
      */
     public function getNonceAction(): string;
 
-    /**
-     * @return string
-     */
-    public function getUniqueId(): string;
-
     /**
      * @return string
      */
     public function getAction(): string;
 
-    /**
-     * @return array
-     */
-    public function getButtons() : array;
-
     /**
      * @return Data|FlexObjectInterface
      */
@@ -94,14 +94,6 @@ interface FlexFormInterface extends \Serializable
      */
     public function getFileDeleteAjaxRoute($field, $filename): ?Route;
 
-    /**
-     * Note: this method clones the object.
-     *
-     * @param FlexObjectInterface $object
-     * @return $this
-     */
-    public function setObject(FlexObjectInterface $object): self;
-
     /**
      * @return FlexObjectInterface
      */
@@ -152,20 +144,6 @@ interface FlexFormInterface extends \Serializable
      */
     public function getBlueprint(): Blueprint;
 
-    /**
-     * Implements \Serializable::serialize().
-     *
-     * @return string
-     */
-    public function serialize(): string;
-
-    /**
-     * Implements \Serializable::unserialize().
-     *
-     * @param string $data
-     */
-    public function unserialize($data): void;
-
     /**
      * @return string
      */
diff --git a/system/src/Grav/Framework/Flex/Storage/AbstractFilesystemStorage.php b/system/src/Grav/Framework/Flex/Storage/AbstractFilesystemStorage.php
index 76dae57b9..ed08e4608 100644
--- a/system/src/Grav/Framework/Flex/Storage/AbstractFilesystemStorage.php
+++ b/system/src/Grav/Framework/Flex/Storage/AbstractFilesystemStorage.php
@@ -15,8 +15,6 @@ use Grav\Common\File\CompiledJsonFile;
 use Grav\Common\File\CompiledMarkdownFile;
 use Grav\Common\File\CompiledYamlFile;
 use Grav\Common\Grav;
-use Grav\Common\Helpers\Base32;
-use Grav\Common\Utils;
 use Grav\Framework\File\Formatter\FormatterInterface;
 use Grav\Framework\File\Formatter\JsonFormatter;
 use Grav\Framework\File\Formatter\MarkdownFormatter;
diff --git a/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php b/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php
index c9a6c7428..907eccec0 100644
--- a/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php
+++ b/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php
@@ -14,7 +14,7 @@ use Grav\Common\Filesystem\Folder;
 use Grav\Common\Grav;
 use Grav\Common\Media\Traits\MediaTrait;
 use Grav\Common\Utils;
-use Grav\Plugin\Form\FormFlashFile;
+use Grav\Framework\Form\FormFlashFile;
 use Psr\Http\Message\UploadedFileInterface;
 use RocketTheme\Toolbox\File\YamlFile;
 use RocketTheme\Toolbox\ResourceLocator\UniformResourceLocator;
@@ -80,7 +80,7 @@ trait FlexMediaTrait
         }
     }
 
-    public function uploadMediaFile(UploadedFileInterface $uploadedFile, string $filename = null) : void
+    public function uploadMediaFile(UploadedFileInterface $uploadedFile, string $filename = null, string $field = null) : void
     {
         $this->checkUploadedMediaFile($uploadedFile);
 
@@ -121,7 +121,7 @@ trait FlexMediaTrait
         $this->clearMediaCache();
     }
 
-    public function deleteMediaFile(string $filename) : void
+    public function deleteMediaFile(string $filename, string $field = null) : void
     {
         $grav = Grav::instance();
         $language = $grav['language'];
diff --git a/system/src/Grav/Framework/Form/FormFlash.php b/system/src/Grav/Framework/Form/FormFlash.php
new file mode 100644
index 000000000..7396f96ab
--- /dev/null
+++ b/system/src/Grav/Framework/Form/FormFlash.php
@@ -0,0 +1,400 @@
+<?php
+
+/**
+ * @package    Grav\Framework\Form
+ *
+ * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
+ * @license    MIT License; see LICENSE file for details.
+ */
+
+namespace Grav\Framework\Form;
+
+use Grav\Common\Filesystem\Folder;
+use Grav\Common\Grav;
+use Grav\Common\Session;
+use Grav\Common\User\User;
+use RocketTheme\Toolbox\File\YamlFile;
+
+class FormFlash implements \JsonSerializable
+{
+    /** @var string */
+    protected $form;
+    /** @var string */
+    protected $uniqueId;
+    /** @var string */
+    protected $url;
+    /** @var array */
+    protected $user;
+    /** @var array */
+    protected $uploads;
+    /** @var array */
+    protected $uploadObjects;
+    /** @var bool */
+    protected $exists;
+
+    /**
+     * FormFlashObject constructor.
+     * @param string $form
+     * @param string $uniqueId
+     */
+    public function __construct(string $form, $uniqueId = null)
+    {
+        $this->form = $form;
+        $this->uniqueId = $uniqueId;
+
+        $file = $this->getTmpIndex();
+        $this->exists = $file->exists();
+
+        $data = $this->exists ? (array)$file->content() : [];
+        $this->url = $data['url'] ?? null;
+        $this->user = $data['user'] ?? null;
+        $this->uploads = $data['uploads'] ?? [];
+    }
+
+    /**
+     * @return string
+     */
+    public function getFormName() : string
+    {
+        return $this->form;
+    }
+
+    /**
+     * @return string
+     */
+    public function getUniqieId() : string
+    {
+        return $this->uniqueId ?? $this->getFormName();
+    }
+
+    /**
+     * @return bool
+     */
+    public function exists() : bool
+    {
+        return $this->exists;
+    }
+
+    /**
+     * @return $this
+     */
+    public function save() : self
+    {
+        $file = $this->getTmpIndex();
+        $file->save($this->jsonSerialize());
+        $this->exists = true;
+
+        return $this;
+    }
+
+    public function delete() : self
+    {
+        $this->removeTmpDir();
+        $this->uploads = [];
+        $this->exists = false;
+
+        return $this;
+    }
+
+    /**
+     * @return string
+     */
+    public function getUrl() : string
+    {
+        return $this->url ?? '';
+    }
+
+    /**
+     * @param string $url
+     * @return $this
+     */
+    public function setUrl(string $url) : self
+    {
+        $this->url = $url;
+
+        return $this;
+    }
+
+    /**
+     * @return string
+     */
+    public function getUsername() : string
+    {
+        return $this->user['username'] ?? '';
+    }
+
+    /**
+     * @return string
+     */
+    public function getUserEmail() : string
+    {
+        return $this->user['email'] ?? '';
+    }
+
+    /**
+     * @param User|null $user
+     * @return $this
+     */
+    public function setUser(?User $user = null) : self
+    {
+        if ($user && $user->username) {
+            $this->user = [
+                'username' => $user->username,
+                'email' => $user->email
+            ];
+        } else {
+            $this->user = null;
+        }
+
+        return $this;
+    }
+
+
+    /**
+     * @param string $field
+     * @return array
+     */
+    public function getFilesByField(string $field) : array
+    {
+        if (!isset($this->uploadObjects[$field])) {
+            $objects = [];
+            foreach ($this->uploads[$field] ?? [] as $filename => $upload) {
+                $objects[$filename] = new FormFlashFile($field, $upload, $this);
+            }
+            $this->uploadObjects[$field] = $objects;
+        }
+
+        return $this->uploadObjects[$field];
+    }
+
+    /**
+     * @return array
+     */
+    public function getFilesByFields() : array
+    {
+        $list = [];
+        foreach ($this->uploads as $field => $values) {
+            if (strpos($field, '/')) {
+                continue;
+            }
+            $list[$field] = $this->getFilesByField($field);
+        }
+
+        return $list;
+    }
+
+    /**
+     * @return array
+     * @deprecated 1.6 For backwards compatibility only, do not use.
+     */
+    public function getLegacyFiles() : array
+    {
+        $fields = [];
+        foreach ($this->uploads as $field => $files) {
+            if (strpos($field, '/')) {
+                continue;
+            }
+            foreach ($files as $file) {
+                $file['tmp_name'] = $this->getTmpDir() . '/' . $file['tmp_name'];
+                $fields[$field][$file['path'] ?? $file['name']] = $file;
+            }
+        }
+
+        return $fields;
+    }
+
+    /**
+     * @param string $field
+     * @param string $filename
+     * @param array $upload
+     * @return bool
+     */
+    public function uploadFile(string $field, string $filename, array $upload) : bool
+    {
+        $tmp_dir = $this->getTmpDir();
+
+        Folder::create($tmp_dir);
+
+        $tmp_file = $upload['file']['tmp_name'];
+        $basename = basename($tmp_file);
+
+        if (!move_uploaded_file($tmp_file, $tmp_dir . '/' . $basename)) {
+            return false;
+        }
+
+        $upload['file']['tmp_name'] = $basename;
+
+        if (!isset($this->uploads[$field])) {
+            $this->uploads[$field] = [];
+        }
+
+        // Prepare object for later save
+        $upload['file']['name'] = $filename;
+
+        // Replace old file, including original
+        $oldUpload = $this->uploads[$field][$filename] ?? null;
+        if (isset($oldUpload['tmp_name'])) {
+            $this->removeTmpFile($oldUpload['tmp_name']);
+        }
+
+        $originalUpload = $this->uploads[$field . '/original'][$filename] ?? null;
+        if (isset($originalUpload['tmp_name'])) {
+            $this->removeTmpFile($originalUpload['tmp_name']);
+            unset($this->uploads[$field . '/original'][$filename]);
+        }
+
+        // Prepare data to be saved later
+        $this->uploads[$field][$filename] = $upload['file'];
+
+        return true;
+    }
+
+    /**
+     * @param string $field
+     * @param string $filename
+     * @param array $upload
+     * @param array $crop
+     * @return bool
+     */
+    public function cropFile(string $field, string $filename, array $upload, array $crop) : bool
+    {
+        $tmp_dir = $this->getTmpDir();
+
+        Folder::create($tmp_dir);
+
+        $tmp_file = $upload['file']['tmp_name'];
+        $basename = basename($tmp_file);
+
+        if (!move_uploaded_file($tmp_file, $tmp_dir . '/' . $basename)) {
+            return false;
+        }
+
+        $upload['file']['tmp_name'] = $basename;
+
+        if (!isset($this->uploads[$field])) {
+            $this->uploads[$field] = [];
+        }
+
+        // Prepare object for later save
+        $upload['file']['name'] = $filename;
+
+        $oldUpload = $this->uploads[$field][$filename] ?? null;
+        if ($oldUpload) {
+            $originalUpload = $this->uploads[$field . '/original'][$filename] ?? null;
+            if ($originalUpload) {
+                $this->removeTmpFile($oldUpload['tmp_name']);
+            } else {
+                $oldUpload['crop'] = $crop;
+                $this->uploads[$field . '/original'][$filename] = $oldUpload;
+            }
+        }
+
+        // Prepare data to be saved later
+        $this->uploads[$field][$filename] = $upload['file'];
+
+        return true;
+    }
+
+    /**
+     * @param string $field
+     * @param string $filename
+     * @return bool
+     */
+    public function removeFile(string $field, string $filename) : bool
+    {
+        if (!$field || !$filename) {
+            return false;
+        }
+
+        $file = $this->getTmpIndex();
+        if (!$file->exists()) {
+            return false;
+        }
+
+        $upload = $this->uploads[$field][$filename] ?? null;
+        if (null !== $upload) {
+            $this->removeTmpFile($upload['tmp_name'] ?? '');
+        }
+        $upload = $this->uploads[$field . '/original'][$filename] ?? null;
+        if (null !== $upload) {
+            $this->removeTmpFile($upload['tmp_name'] ?? '');
+        }
+
+        // Walk backward to cleanup any empty field that's left
+        unset(
+            $this->uploadObjects[$field][$filename],
+            $this->uploads[$field][$filename],
+            $this->uploadObjects[$field . '/original'][$filename],
+            $this->uploads[$field . '/original'][$filename]
+        );
+        if (empty($this->uploads[$field])) {
+            unset($this->uploads[$field]);
+        }
+        if (empty($this->uploads[$field . '/original'])) {
+            unset($this->uploads[$field . '/original']);
+        }
+
+        return true;
+    }
+
+    /**
+     * @return array
+     */
+    public function jsonSerialize() : array
+    {
+        return [
+            'form' => $this->form,
+            'unique_id' => $this->uniqueId,
+            'url' => $this->url,
+            'user' => $this->user,
+            'uploads' => $this->uploads
+        ];
+    }
+
+    /**
+     * @return string
+     */
+    public function getTmpDir() : string
+    {
+        $grav = Grav::instance();
+
+        /** @var Session $session */
+        $session = $grav['session'];
+
+        $location = [
+            'forms',
+            $session->getId(),
+            $this->uniqueId ?: $this->form
+        ];
+
+        return $grav['locator']->findResource('tmp://', true, true) . '/' . implode('/', $location);
+    }
+
+    /**
+     * @return YamlFile
+     */
+    protected function getTmpIndex() : YamlFile
+    {
+        // Do not use CompiledYamlFile as the file can change multiple times per second.
+        return YamlFile::instance($this->getTmpDir() . '/index.yaml');
+    }
+
+    /**
+     * @param string $name
+     */
+    protected function removeTmpFile(string $name) : void
+    {
+        $filename = $this->getTmpDir() . '/' . $name;
+        if ($name && is_file($filename)) {
+            unlink($filename);
+        }
+    }
+
+    protected function removeTmpDir() : void
+    {
+        $tmpDir = $this->getTmpDir();
+        if (file_exists($tmpDir)) {
+            Folder::delete($tmpDir);
+        }
+    }
+}
diff --git a/system/src/Grav/Framework/Form/FormFlashFile.php b/system/src/Grav/Framework/Form/FormFlashFile.php
new file mode 100644
index 000000000..2cb78d016
--- /dev/null
+++ b/system/src/Grav/Framework/Form/FormFlashFile.php
@@ -0,0 +1,146 @@
+<?php
+
+/**
+ * @package    Grav\Framework\Form
+ *
+ * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
+ * @license    MIT License; see LICENSE file for details.
+ */
+
+namespace Grav\Framework\Form;
+
+use Grav\Framework\Psr7\Stream;
+use Psr\Http\Message\StreamInterface;
+use Psr\Http\Message\UploadedFileInterface;
+
+class FormFlashFile implements UploadedFileInterface, \JsonSerializable
+{
+    private $field;
+    private $moved = false;
+    private $upload;
+    private $flash;
+
+    public function __construct(string $field, array $upload, FormFlash $flash)
+    {
+        $this->field = $field;
+        $this->upload = $upload;
+        $this->flash = $flash;
+
+        if ($this->isOk() && (empty($this->upload['tmp_name']) || !file_exists($this->getTmpFile()))) {
+            $this->upload['error'] = \UPLOAD_ERR_NO_FILE;
+        }
+
+        if (!isset($this->upload['size'])) {
+            $this->upload['size'] =  $this->isOk() ? filesize($this->getTmpFile()) : 0;
+        }
+    }
+
+    /**
+     * @return StreamInterface
+     */
+    public function getStream()
+    {
+        $this->validateActive();
+
+        $resource = \fopen($this->getTmpFile(), 'rb');
+
+        return Stream::create($resource);
+    }
+
+    public function moveTo($targetPath)
+    {
+        $this->validateActive();
+
+        if (!\is_string($targetPath) || empty($targetPath)) {
+            throw new \InvalidArgumentException('Invalid path provided for move operation; must be a non-empty string');
+        }
+
+        $this->moved = \copy($this->getTmpFile(), $targetPath);
+
+        if (false === $this->moved) {
+            throw new \RuntimeException(\sprintf('Uploaded file could not be moved to %s', $targetPath));
+        }
+
+        $this->flash->removeFile($this->field, $this->upload['tmp_name']);
+    }
+
+    public function getSize()
+    {
+        return $this->upload['size'];
+    }
+
+    public function getError()
+    {
+        return $this->upload['error'] ?? \UPLOAD_ERR_OK;
+    }
+
+    public function getClientFilename()
+    {
+        return $this->upload['name'] ?? 'unknown';
+    }
+
+    public function getClientMediaType()
+    {
+        return $this->upload['type'] ?? 'application/octet-stream';
+    }
+
+    public function isMoved() : bool
+    {
+        return $this->moved;
+    }
+
+    public function getMetaData() : array
+    {
+        if (isset($this->upload['crop'])) {
+            return ['crop' => $this->upload['crop']];
+        }
+
+        return [];
+    }
+
+    public function getDestination()
+    {
+        return $this->upload['path'];
+    }
+
+    public function jsonSerialize()
+    {
+        return $this->upload;
+    }
+
+    public function __debugInfo()
+    {
+        return [
+            'field:private' => $this->field,
+            'moved:private' => $this->moved,
+            'upload:private' => $this->upload,
+        ];
+    }
+
+    /**
+     * @throws \RuntimeException if is moved or not ok
+     */
+    private function validateActive(): void
+    {
+        if (!$this->isOk()) {
+            throw new \RuntimeException('Cannot retrieve stream due to upload error');
+        }
+
+        if ($this->moved) {
+            throw new \RuntimeException('Cannot retrieve stream after it has already been moved');
+        }
+    }
+
+    /**
+     * @return bool return true if there is no upload error
+     */
+    private function isOk(): bool
+    {
+        return \UPLOAD_ERR_OK === $this->getError();
+    }
+
+    private function getTmpFile() : string
+    {
+        return $this->flash->getTmpDir() . '/' . $this->upload['tmp_name'];
+    }
+}
diff --git a/system/src/Grav/Framework/Object/Base/ObjectTrait.php b/system/src/Grav/Framework/Object/Base/ObjectTrait.php
index 395e6ad3d..4b4a4fa65 100644
--- a/system/src/Grav/Framework/Object/Base/ObjectTrait.php
+++ b/system/src/Grav/Framework/Object/Base/ObjectTrait.php
@@ -140,7 +140,7 @@ trait ObjectTrait
      */
     protected function doSerialize()
     {
-        return $this->jsonSerialize();
+        return ['key' => $this->getKey(), 'type' => $this->getType(), 'elements' => $this->getElements()];
     }
 
     /**
@@ -163,7 +163,7 @@ trait ObjectTrait
      */
     public function jsonSerialize()
     {
-        return ['key' => $this->getKey(), 'type' => $this->getType(), 'elements' => $this->getElements()];
+        return $this->doSerialize();
     }
 
     /**
diff --git a/system/src/Grav/Framework/Psr7/Request.php b/system/src/Grav/Framework/Psr7/Request.php
index 7e1fd6b93..f6c26ae4d 100644
--- a/system/src/Grav/Framework/Psr7/Request.php
+++ b/system/src/Grav/Framework/Psr7/Request.php
@@ -1,3 +1,3 @@
 <?php
 
-class_alias('Nyholm\Psr7\Request', 'Grav\Framework\Psr7\Request');
+class_alias(Nyholm\Psr7\Request::class, Grav\Framework\Psr7\Request::class);
diff --git a/system/src/Grav/Framework/Psr7/Response.php b/system/src/Grav/Framework/Psr7/Response.php
index 222312c5e..00270e42a 100644
--- a/system/src/Grav/Framework/Psr7/Response.php
+++ b/system/src/Grav/Framework/Psr7/Response.php
@@ -1,3 +1,3 @@
 <?php
 
-class_alias('Nyholm\Psr7\Response', 'Grav\Framework\Psr7\Response');
+class_alias(Nyholm\Psr7\Response::class, Grav\Framework\Psr7\Response::class);
diff --git a/system/src/Grav/Framework/Psr7/ServerRequest.php b/system/src/Grav/Framework/Psr7/ServerRequest.php
index e217b536d..0e55052b9 100644
--- a/system/src/Grav/Framework/Psr7/ServerRequest.php
+++ b/system/src/Grav/Framework/Psr7/ServerRequest.php
@@ -1,3 +1,3 @@
 <?php
 
-class_alias('Nyholm\Psr7\ServerRequest', 'Grav\Framework\Psr7\ServerRequest');
+class_alias(Nyholm\Psr7\ServerRequest::class, Grav\Framework\Psr7\ServerRequest::class);
diff --git a/system/src/Grav/Framework/Psr7/Stream.php b/system/src/Grav/Framework/Psr7/Stream.php
index eb2661404..470491f18 100644
--- a/system/src/Grav/Framework/Psr7/Stream.php
+++ b/system/src/Grav/Framework/Psr7/Stream.php
@@ -1,3 +1,3 @@
 <?php
 
-class_alias('Nyholm\Psr7\Stream', 'Grav\Framework\Psr7\Stream');
+class_alias(Nyholm\Psr7\Stream::class, Grav\Framework\Psr7\Stream::class);
diff --git a/system/src/Grav/Framework/Psr7/UploadedFile.php b/system/src/Grav/Framework/Psr7/UploadedFile.php
index 52989905f..9c057ddcf 100644
--- a/system/src/Grav/Framework/Psr7/UploadedFile.php
+++ b/system/src/Grav/Framework/Psr7/UploadedFile.php
@@ -1,3 +1,3 @@
 <?php
 
-class_alias('Nyholm\Psr7\UploadedFile', 'Grav\Framework\Psr7\UploadedFile');
+class_alias(Nyholm\Psr7\UploadedFile::class, Grav\Framework\Psr7\UploadedFile::class);
diff --git a/system/src/Grav/Framework/Psr7/Uri.php b/system/src/Grav/Framework/Psr7/Uri.php
index 6676dc2d7..ebf46728f 100644
--- a/system/src/Grav/Framework/Psr7/Uri.php
+++ b/system/src/Grav/Framework/Psr7/Uri.php
@@ -1,3 +1,3 @@
 <?php
 
-class_alias('Nyholm\Psr7\Uri', 'Grav\Framework\Psr7\Uri');
+class_alias(Nyholm\Psr7\Uri::class, Grav\Framework\Psr7\Uri::class);
diff --git a/system/src/Grav/Framework/RequestHandler/Exception/NotHandledException.php b/system/src/Grav/Framework/RequestHandler/Exception/NotHandledException.php
index b5d08148f..f36680165 100644
--- a/system/src/Grav/Framework/RequestHandler/Exception/NotHandledException.php
+++ b/system/src/Grav/Framework/RequestHandler/Exception/NotHandledException.php
@@ -11,17 +11,6 @@ declare(strict_types=1);
 
 namespace Grav\Framework\RequestHandler\Exception;
 
-use Psr\Http\Message\ServerRequestInterface;
-
 class NotHandledException extends NotFoundException
 {
-    /**
-     * NotFoundException constructor.
-     * @param ServerRequestInterface $request
-     * @param \Throwable|null $previous
-     */
-    public function __construct(ServerRequestInterface $request, \Throwable $previous = null)
-    {
-        parent::__construct($request, $previous);
-    }
 }
diff --git a/system/src/Grav/Framework/Session/SessionInterface.php b/system/src/Grav/Framework/Session/SessionInterface.php
index be3462015..a63d54c45 100644
--- a/system/src/Grav/Framework/Session/SessionInterface.php
+++ b/system/src/Grav/Framework/Session/SessionInterface.php
@@ -111,7 +111,7 @@ interface SessionInterface extends \IteratorAggregate
     /**
      * Checks if the session was started.
      *
-     * @return Boolean
+     * @return bool
      */
     public function isStarted();
 
diff --git a/tests/unit/Grav/Framework/Filesystem/FilesystemTest.php b/tests/unit/Grav/Framework/Filesystem/FilesystemTest.php
new file mode 100644
index 000000000..8e4e37c73
--- /dev/null
+++ b/tests/unit/Grav/Framework/Filesystem/FilesystemTest.php
@@ -0,0 +1,322 @@
+<?php
+
+use Grav\Framework\Filesystem\Filesystem;
+
+class FilesystemTest extends \Codeception\TestCase\Test
+{
+    protected $class;
+
+    protected $tests = [
+        '' => [
+            'parent' => '',
+            'normalize' => '',
+            'dirname' => '',
+            'pathinfo' => [
+                'basename' => '',
+                'filename' => '',
+            ]
+        ],
+        '.' => [
+            'parent' => '',
+            'normalize' => '',
+            'dirname' => '.',
+            'pathinfo' => [
+                'dirname' => '.',
+                'basename' => '.',
+                'extension' => '',
+                'filename' => '',
+            ]
+        ],
+        './' => [
+            'parent' => '',
+            'normalize' => '',
+            'dirname' => '.',
+            'pathinfo' => [
+                'dirname' => '.',
+                'basename' => '.',
+                'extension' => '',
+                'filename' => '',
+
+            ]
+        ],
+        '././.' => [
+            'parent' => '',
+            'normalize' => '',
+            'dirname' => './.',
+            'pathinfo' => [
+                'dirname' => './.',
+                'basename' => '.',
+                'extension' => '',
+                'filename' => '',
+            ]
+        ],
+        '.file' => [
+            'parent' => '.',
+            'normalize' => '.file',
+            'dirname' => '.',
+            'pathinfo' => [
+                'dirname' => '.',
+                'basename' => '.file',
+                'extension' => 'file',
+                'filename' => '',
+            ]
+        ],
+        '/' => [
+            'parent' => '',
+            'normalize' => '/',
+            'dirname' => '/',
+            'pathinfo' => [
+                'dirname' => '/',
+                'basename' => '',
+                'filename' => '',
+            ]
+        ],
+        '/absolute' => [
+            'parent' => '/',
+            'normalize' => '/absolute',
+            'dirname' => '/',
+            'pathinfo' => [
+                'dirname' => '/',
+                'basename' => 'absolute',
+                'filename' => 'absolute',
+            ]
+        ],
+        '/absolute/' => [
+            'parent' => '/',
+            'normalize' => '/absolute',
+            'dirname' => '/',
+            'pathinfo' => [
+                'dirname' => '/',
+                'basename' => 'absolute',
+                'filename' => 'absolute',
+            ]
+        ],
+        '/very/long/absolute/path' => [
+            'parent' => '/very/long/absolute',
+            'normalize' => '/very/long/absolute/path',
+            'dirname' => '/very/long/absolute',
+            'pathinfo' => [
+                'dirname' => '/very/long/absolute',
+                'basename' => 'path',
+                'filename' => 'path',
+            ]
+        ],
+        'relative' => [
+            'parent' => '.',
+            'normalize' => 'relative',
+            'dirname' => '.',
+            'pathinfo' => [
+                'dirname' => '.',
+                'basename' => 'relative',
+                'filename' => 'relative',
+            ]
+        ],
+        'very/long/relative/path' => [
+            'parent' => 'very/long/relative',
+            'normalize' => 'very/long/relative/path',
+            'dirname' => 'very/long/relative',
+            'pathinfo' => [
+                'dirname' => 'very/long/relative',
+                'basename' => 'path',
+                'filename' => 'path',
+            ]
+        ],
+        'path/to/file.jpg' => [
+            'parent' => 'path/to',
+            'normalize' => 'path/to/file.jpg',
+            'dirname' => 'path/to',
+            'pathinfo' => [
+                'dirname' => 'path/to',
+                'basename' => 'file.jpg',
+                'extension' => 'jpg',
+                'filename' => 'file',
+            ]
+        ],
+        'user://' => [
+            'parent' => '',
+            'normalize' => 'user://',
+            'dirname' => 'user://',
+            'pathinfo' => [
+                'dirname' => 'user://',
+                'basename' => '',
+                'filename' => '',
+                'scheme' => 'user',
+            ]
+        ],
+        'user://.' => [
+            'parent' => '',
+            'normalize' => 'user://',
+            'dirname' => 'user://',
+            'pathinfo' => [
+                'dirname' => 'user://',
+                'basename' => '',
+                'filename' => '',
+                'scheme' => 'user',
+            ]
+        ],
+        'user://././.' => [
+            'parent' => '',
+            'normalize' => 'user://',
+            'dirname' => 'user://',
+            'pathinfo' => [
+                'dirname' => 'user://',
+                'basename' => '',
+                'filename' => '',
+                'scheme' => 'user',
+            ]
+        ],
+        'user://./././file' => [
+            'parent' => 'user://',
+            'normalize' => 'user://file',
+            'dirname' => 'user://',
+            'pathinfo' => [
+                'dirname' => 'user://',
+                'basename' => 'file',
+                'filename' => 'file',
+                'scheme' => 'user',
+            ]
+        ],
+        'user://./././folder/file' => [
+            'parent' => 'user://folder',
+            'normalize' => 'user://folder/file',
+            'dirname' => 'user://folder',
+            'pathinfo' => [
+                'dirname' => 'user://folder',
+                'basename' => 'file',
+                'filename' => 'file',
+                'scheme' => 'user',
+            ]
+        ],
+        'user://.file' => [
+            'parent' => 'user://',
+            'normalize' => 'user://.file',
+            'dirname' => 'user://',
+            'pathinfo' => [
+                'dirname' => 'user://',
+                'basename' => '.file',
+                'extension' => 'file',
+                'filename' => '',
+                'scheme' => 'user',
+            ]
+        ],
+        'user:///' => [
+            'parent' => '',
+            'normalize' => 'user:///',
+            'dirname' => 'user:///',
+            'pathinfo' => [
+                'dirname' => 'user:///',
+                'basename' => '',
+                'filename' => '',
+                'scheme' => 'user',
+            ]
+        ],
+        'user:///absolute' => [
+            'parent' => 'user:///',
+            'normalize' => 'user:///absolute',
+            'dirname' => 'user:///',
+            'pathinfo' => [
+                'dirname' => 'user:///',
+                'basename' => 'absolute',
+                'filename' => 'absolute',
+                'scheme' => 'user',
+            ]
+        ],
+        'user:///very/long/absolute/path' => [
+            'parent' => 'user:///very/long/absolute',
+            'normalize' => 'user:///very/long/absolute/path',
+            'dirname' => 'user:///very/long/absolute',
+            'pathinfo' => [
+                'dirname' => 'user:///very/long/absolute',
+                'basename' => 'path',
+                'filename' => 'path',
+                'scheme' => 'user',
+            ]
+        ],
+        'user://relative' => [
+            'parent' => 'user://',
+            'normalize' => 'user://relative',
+            'dirname' => 'user://',
+            'pathinfo' => [
+                'dirname' => 'user://',
+                'basename' => 'relative',
+                'filename' => 'relative',
+                'scheme' => 'user',
+            ]
+        ],
+        'user://very/long/relative/path' => [
+            'parent' => 'user://very/long/relative',
+            'normalize' => 'user://very/long/relative/path',
+            'dirname' => 'user://very/long/relative',
+            'pathinfo' => [
+                'dirname' => 'user://very/long/relative',
+                'basename' => 'path',
+                'filename' => 'path',
+                'scheme' => 'user',
+            ]
+        ],
+        'user://path/to/file.jpg' => [
+            'parent' => 'user://path/to',
+            'normalize' => 'user://path/to/file.jpg',
+            'dirname' => 'user://path/to',
+            'pathinfo' => [
+                'dirname' => 'user://path/to',
+                'basename' => 'file.jpg',
+                'extension' => 'jpg',
+                'filename' => 'file',
+                'scheme' => 'user',
+            ]
+        ],
+    ];
+
+    protected function _before()
+    {
+        $this->class = new Filesystem();
+    }
+
+    protected function _after()
+    {
+        unset($this->class);
+    }
+
+    protected function runTestSet(array $tests, $method)
+    {
+        $class = $this->class;
+        foreach ($tests as $path => $candidates) {
+            if (!array_key_exists($method, $candidates)) {
+                continue;
+            }
+
+            $expected = $candidates[$method];
+
+            $result = $class->{$method}($path);
+
+            $this->assertSame($expected, $result, "Test {$method}('{$path}')");
+
+            if (function_exists($method) && !strpos($path, '://')) {
+                $cmp_result = $method($path);
+
+                $this->assertSame($cmp_result, $result, "Compare to original {$method}('{$path}')");
+            }
+        }
+    }
+
+    public function testParent()
+    {
+        $this->runTestSet($this->tests, 'parent');
+    }
+
+    public function testNormalize()
+    {
+        $this->runTestSet($this->tests, 'normalize');
+    }
+
+    public function testDirname()
+    {
+        $this->runTestSet($this->tests, 'dirname');
+    }
+
+    public function testPathinfo()
+    {
+        $this->runTestSet($this->tests, 'pathinfo');
+    }
+}