diff --git a/composer.json b/composer.json
index 3ad256f..679d496 100644
--- a/composer.json
+++ b/composer.json
@@ -7,7 +7,7 @@
         "email": "morlokdk@gmail.com"
     }],
     "require": {
-        "php": ">=5.4.0",
+        "php": ">=5.6.0",
         "nette/utils": "^2.3",
         "nette/safe-stream": "^2.3"
     },
diff --git a/src/Localization/LocalizationExtension.php b/src/Localization/LocalizationExtension.php
index 78caf8c..8e54f61 100644
--- a/src/Localization/LocalizationExtension.php
+++ b/src/Localization/LocalizationExtension.php
@@ -3,56 +3,54 @@
 namespace Smartsupp\Localization;
 
 use Nette\DI\CompilerExtension;
+use Nette\Utils\Validators;
 
 class LocalizationExtension extends CompilerExtension
 {
 
 	public $defaults = [
+		'tempDir' => '%tempDir%/cache/Localization',
 		'translatesDir' => null,
-		'debugMode' => null,
-		'sections' => null,
-		'alias' => null,
+		'debugMode' => '%debugMode%',
+		'sections' => [],
+		'alias' => [],
 		'parameters' => [],
+		'filters' => [],
 	];
 
-	private $tempDir;
-
-
-	public function __construct($tempDir = null)
-	{
-		$this->tempDir = $tempDir;
-	}
-
 
 	public function loadConfiguration()
 	{
 		$container = $this->getContainerBuilder();
 		$config = $this->getConfig($this->defaults);
-		$debugMode = $config['debugMode'] !== null ? $config['debugMode'] : $container->parameters['debugMode'];
-		$tempDir = $this->tempDir ? $this->tempDir : $container->parameters['tempDir'];
+
+		Validators::assertField($config, 'translatesDir', 'string');
 
 		$container->addDefinition($this->prefix('translatesStorage'))
-			->setClass('Smartsupp\Localization\DirectoryStorage')
+			->setClass(DirectoryStorage::class)
 			->setArguments([$config['translatesDir']]);
 
 		$container->addDefinition($this->prefix('translatesLoader'))
-			->setClass('Smartsupp\Localization\TranslatesLoader')
-			->addSetup('$debugMode', [$debugMode])
-			->addSetup('setTempDir', [$tempDir . '/cache/_Wimo.Localization']);
+			->setClass(TranslatesLoader::class)
+			->addSetup('$debugMode', [$config['debugMode']])
+			->addSetup('setTempDir', [$config['tempDir']]);
 
 		$translatorFactory = $container->addDefinition($this->prefix('translatorFactory'))
-			->setClass('Smartsupp\Localization\TranslatorFactory')
-			->addSetup('$debugMode', [$debugMode])
+			->setClass(TranslatorFactory::class)
+			->addSetup('$defaultSections', [$config['sections']])
 			->addSetup('setParameters', [$config['parameters']]);
 
-		if ($config['sections']) {
-			$translatorFactory->addSetup('$defaultSections', [$config['sections']]);
-		}
-		if ($config['alias']) {
+		if (count($config['alias'])) {
 			foreach ($config['alias'] as $from => $to) {
 				$translatorFactory->addSetup('setAlias', [$from, $to]);
 			}
 		}
+
+		if (count($config['filters'])) {
+			foreach ($config['filters'] as $filter) {
+				$translatorFactory->addSetup('addFilter', [$filter]);
+			}
+		}
 	}
 
 }
diff --git a/src/Localization/Translator.php b/src/Localization/Translator.php
index 7fd9f96..963b50f 100644
--- a/src/Localization/Translator.php
+++ b/src/Localization/Translator.php
@@ -2,18 +2,20 @@
 
 namespace Smartsupp\Localization;
 
+use Nette\Utils\Validators;
+
 class Translator implements ITranslator
 {
 
-	/** @var boolean */
-	public $debugMode = false;
-
 	/** @var array  translation table */
 	private $dictionary = [];
 
 	/** @var array */
 	private $parameters = [];
 
+	/** @var array */
+	private $filters = [];
+
 
 	/**
 	 * Set dictionary
@@ -53,6 +55,18 @@ public function getParameters()
 	}
 
 
+	/**
+	 * @param callable $filter
+	 */
+	public function addFilter($filter)
+	{
+		if (!Validators::isCallable($filter)) {
+			throw new \Nette\Utils\AssertionException("Filter is not callable");
+		}
+		$this->filters[] = $filter;
+	}
+
+
 	/**
 	 * Has message?
 	 * @param string $key
@@ -92,11 +106,19 @@ public function translate($key, $args = null)
 			}
 		}
 
-		return $this->replaceParameters($message);
+		if (count($this->parameters) > 0) {
+			$message = $this->applyParameters($message);
+		}
+
+		foreach ($this->filters as $filter) {
+			$message = call_user_func_array($filter, [$message, $key]);
+		}
+
+		return $message;
 	}
 
 
-	private function replaceParameters($string)
+	private function applyParameters($string)
 	{
 		if (strpos($string, '{') === false) {
 			return $string;
@@ -105,8 +127,7 @@ private function replaceParameters($string)
 			if (!isset($this->parameters[$matches[1]])) {
 				return $matches[0];
 			} else {
-				// TODO: prevent cyclic replacing
-				return $this->replaceParameters($this->parameters[$matches[1]]);
+				return $this->applyParameters($this->parameters[$matches[1]]);
 			}
 		}, $string);
 	}
diff --git a/src/Localization/TranslatorFactory.php b/src/Localization/TranslatorFactory.php
index 44f601c..7d318cd 100644
--- a/src/Localization/TranslatorFactory.php
+++ b/src/Localization/TranslatorFactory.php
@@ -2,12 +2,11 @@
 
 namespace Smartsupp\Localization;
 
+use Nette\Utils\Validators;
+
 class TranslatorFactory
 {
 
-	/** @var boolean */
-	public $debugMode = false;
-
 	/** @var array */
 	public $alias = [];
 
@@ -20,6 +19,9 @@ class TranslatorFactory
 	/** @var array */
 	private $parameters = [];
 
+	/** @var array */
+	private $filters = [];
+
 	/** @var TranslatesLoader */
 	private $loader;
 
@@ -53,6 +55,18 @@ public function setParameters(array $parameters)
 	}
 
 
+	/**
+	 * @param callable $filter
+	 */
+	public function addFilter($filter)
+	{
+		if (!Validators::isCallable($filter)) {
+			throw new \Nette\Utils\AssertionException("Filter is not callable");
+		}
+		$this->filters[] = $filter;
+	}
+
+
 	/**
 	 * @param string $lang
 	 * @param array $sections
@@ -61,10 +75,11 @@ public function setParameters(array $parameters)
 	public function create($lang, array $sections = [])
 	{
 		$translator = new Translator();
-		$translator->debugMode = $this->debugMode;
-
 		$translator->setParameters(['lang' => $lang]);
 		$translator->setParameters($this->parameters);
+		foreach ($this->filters as $filter) {
+			$translator->addFilter($filter);
+		}
 
 		if (isset($this->alias[$lang])) {
 			$lang = $this->alias[$lang];