diff --git a/LANG/de.php b/LANG/de.php
new file mode 100644
index 0000000..118c0f9
--- /dev/null
+++ b/LANG/de.php
@@ -0,0 +1,17 @@
+<?php
+/************************************************|
+|* Beschreibung | Sprachdatei - DEUTSCH         *|
+|************************************************/
+
+ define('LANG', array(
+    /* Validierungsfehler */
+    "val_errors" => [
+        "val_pattern" => "Ungültiges Datenformat.",
+        "val_required" => "Dieses Feld ist erforderlich.",
+        "val_min" => "Der Wert ist zu klein.",
+        "val_max" => "Der Wert ist zu groß.",
+        "val_equal" => "Der Wert sollte gleich sein wie ",
+        "val_file_max_size" => "Die Datei ist zu groß.",
+        "val_file_ext" => "Ungültiges Dateiformat.",
+    ],
+));
diff --git a/LANG/en.php b/LANG/en.php
new file mode 100644
index 0000000..5bb0249
--- /dev/null
+++ b/LANG/en.php
@@ -0,0 +1,17 @@
+<?php
+/************************************************|
+|* Description | Language file - ENGLISH        *|
+|************************************************/
+
+ define('LANG', array(
+  /* Validation errors */
+  "val_errors" => [
+    "val_pattern" => "Invalid data format.",
+    "val_required" => "This field is required.",
+    "val_min" => "The value is too small.",
+    "val_max" => "The value is too large.",
+    "val_equal" => "The value should be equal to ",
+    "val_file_max_size" => "The file is too large.",
+    "val_file_ext" => "Invalid file format.",
+  ],
+));
diff --git a/LANG/es.php b/LANG/es.php
new file mode 100644
index 0000000..35d1d5a
--- /dev/null
+++ b/LANG/es.php
@@ -0,0 +1,17 @@
+<?php
+/************************************************|
+|* Descripción | Archivo de idioma - ESPAÑOL     *|
+|************************************************/
+
+ define('LANG', array(
+    /* Validation errors */
+    "val_errors" => [
+        "val_pattern" => "Formato de datos inválido.",
+        "val_required" => "Este campo es obligatorio.",
+        "val_min" => "El valor es demasiado pequeño.",
+        "val_max" => "El valor es demasiado grande.",
+        "val_equal" => "El valor debe ser igual a ",
+        "val_file_max_size" => "El archivo es demasiado grande.",
+        "val_file_ext" => "Formato de archivo inválido.",
+    ],
+));
diff --git a/LANG/fr.php b/LANG/fr.php
new file mode 100644
index 0000000..64ced36
--- /dev/null
+++ b/LANG/fr.php
@@ -0,0 +1,18 @@
+<?php
+/************************************************|
+|* Description | Fichier de langue - Français   *|
+|************************************************/
+
+    /* Général */
+ define('LANG', array(
+    /* Erreurs de validation */
+    "val_errors" => [
+        "val_pattern" => "Format de données invalide.",
+        "val_required" => "Ce champ est requis.",
+        "val_min" => "La valeur est trop petite.",
+        "val_max" => "La valeur est trop grande.",
+        "val_equal" => "La valeur doit être égale à ",
+        "val_file_max_size" => "Le fichier est trop volumineux.",
+        "val_file_ext" => "Format de fichier invalide.",
+    ],
+));
diff --git a/LANG/it.php b/LANG/it.php
new file mode 100644
index 0000000..df78bbf
--- /dev/null
+++ b/LANG/it.php
@@ -0,0 +1,18 @@
+<?php
+/************************************************|
+|* Descrizione | File di lingua - ITALIANO       *|
+|************************************************/
+
+    /* Generale */
+ define('LANG', array(
+    /* Errori di validazione */
+    "val_errors" => [
+        "val_pattern" => "Formato dati non valido.",
+        "val_required" => "Questo campo è obbligatorio.",
+        "val_min" => "Il valore è troppo piccolo.",
+        "val_max" => "Il valore è troppo grande.",
+        "val_equal" => "Il valore dovrebbe essere uguale a ",
+        "val_file_max_size" => "Il file è troppo grande.",
+        "val_file_ext" => "Formato file non valido.",
+    ],
+));
diff --git a/LANG/pl.php b/LANG/pl.php
new file mode 100644
index 0000000..b0f114e
--- /dev/null
+++ b/LANG/pl.php
@@ -0,0 +1,18 @@
+<?php
+/************************************************|
+|* Description | Plik językowy - POLSKI         *|
+|************************************************/
+
+/* General */
+ define('LANG', array(
+  /* Validation errors */
+  "val_errors" => [
+    "val_pattern" => "Niepoprawny format danych.",
+    "val_required" => "Pole jest wymagane.",
+    "val_min" => "Wartość jest zbyt mała.",
+    "val_max" => "Wartość jest zbyt duza.",
+    "val_equal" => "Wartość powinna być równa ",
+    "val_file_max_size" => "Plik jest zbyt duży.",
+    "val_file_ext" => "Niedozwolony format pliku.",
+  ],
+));
diff --git a/LANG/pt.php b/LANG/pt.php
new file mode 100644
index 0000000..446fdb0
--- /dev/null
+++ b/LANG/pt.php
@@ -0,0 +1,18 @@
+<?php
+/************************************************|
+|* Descrição | Arquivo de idioma - PORTUGUÊS     *|
+|************************************************/
+
+    /* Geral */
+ define('LANG', array(
+    /* Erros de validação */
+    "val_errors" => [
+        "val_pattern" => "Formato de dados inválido.",
+        "val_required" => "Este campo é obrigatório.",
+        "val_min" => "O valor é muito pequeno.",
+        "val_max" => "O valor é muito grande.",
+        "val_equal" => "O valor deve ser igual a ",
+        "val_file_max_size" => "O arquivo é muito grande.",
+        "val_file_ext" => "Formato de arquivo inválido.",
+    ],
+));
diff --git a/LANG/ru.php b/LANG/ru.php
new file mode 100644
index 0000000..7fe4c17
--- /dev/null
+++ b/LANG/ru.php
@@ -0,0 +1,17 @@
+<?php
+/************************************************|
+|* Описание | Файл языка - РУССКИЙ               *|
+|************************************************/
+
+ define('LANG', array(
+    /* Ошибки валидации */
+    "val_errors" => [
+        "val_pattern" => "Неверный формат данных.",
+        "val_required" => "Это поле обязательно для заполнения.",
+        "val_min" => "Значение слишком маленькое.",
+        "val_max" => "Значение слишком большое.",
+        "val_equal" => "Значение должно быть равным ",
+        "val_file_max_size" => "Файл слишком большой.",
+        "val_file_ext" => "Неверный формат файла.",
+    ],
+));
diff --git a/Validation.php b/Validation.php
index f3650cc..e5d1e11 100644
--- a/Validation.php
+++ b/Validation.php
@@ -1,389 +1,433 @@
 <?php
+
+/* Add language files 
+   Available languages: de, en, es, fr, it, pl, pt, ru */
+   
+require_once 'LANG/en.php';
+
+/**
+ * Validation
+ *
+ * Simple PHP class for validation.
+ *
+ * @package Core
+ * @author Davide Cesarano <davide.cesarano@unipegaso.it>
+ * @license https://github.com/davidecesarano/Validation/blob/master/LICENSE MIT License
+ * @link https://github.com/davidecesarano/Validation
+ */
+
+class Validation {
+
+    /**
+     * @var array $patterns
+     */
+    public $patterns = array(
+        'uri'           => '[A-Za-z0-9-\/_?&=]+',
+        'url'           => '[A-Za-z0-9-:.\/_?&=#]+',
+        'alpha'         => '[\p{L}]+',
+        'words'         => '[\p{L}\s]+',
+        'alphanum'      => '[\p{L}0-9]+',
+        'int'           => '[0-9]+',
+        'float'         => '[0-9\.,]+',
+        'tel'           => '[0-9+\s()-]+',
+        'text'          => '[\p{L}0-9\s-.,;:!"%&()?+\'°#\/@]+',
+        'file'          => '[\p{L}\s0-9-_!%&()=\[\]#@,.;+]+\.[A-Za-z0-9]{2,4}',
+        'folder'        => '[\p{L}\s0-9-_!%&()=\[\]#@,.;+]+',
+        'address'       => '[\p{L}0-9\s.,()°-]+',
+        'date_dmy'      => '[0-9]{1,2}\-[0-9]{1,2}\-[0-9]{4}',
+        'date_ymd'      => '[0-9]{4}\-[0-9]{1,2}\-[0-9]{1,2}'
+    );
+
+    /**
+     * @var array $errors
+     */
+    public $errors = array();
+
+    /**
+     * @var mixed $value
+     */
+    public $value = null;
+
+    /**
+     * @var string $name
+     */
+    public $name = null;
+
+    /**
+     * @var mixed $file
+     */
+    public $file = null;
     
+
     /**
-     * Validation 
+     * Field name
      *
-     * Semplice classe PHP per la validazione.
+     * @param string $name
+     * @return self
+     */
+    public function name(string $name) : Validation
+    {
+        $this->name = $name;
+        return $this;
+    }
+
+    /**
+     * Field value
      *
-     * @author Davide Cesarano <davide.cesarano@unipegaso.it>
-     * @copyright (c) 2016, Davide Cesarano
-     * @license https://github.com/davidecesarano/Validation/blob/master/LICENSE MIT License
-     * @link https://github.com/davidecesarano/Validation
+     * @param mixed $value
+     * @return self
      */
-     
-    class Validation {
-        
-        /**
-         * @var array $patterns
-         */
-        public $patterns = array(
-            'uri'           => '[A-Za-z0-9-\/_?&=]+',
-            'url'           => '[A-Za-z0-9-:.\/_?&=#]+',
-            'alpha'         => '[\p{L}]+',
-            'words'         => '[\p{L}\s]+',
-            'alphanum'      => '[\p{L}0-9]+',
-            'int'           => '[0-9]+',
-            'float'         => '[0-9\.,]+',
-            'tel'           => '[0-9+\s()-]+',
-            'text'          => '[\p{L}0-9\s-.,;:!"%&()?+\'°#\/@]+',
-            'file'          => '[\p{L}\s0-9-_!%&()=\[\]#@,.;+]+\.[A-Za-z0-9]{2,4}',
-            'folder'        => '[\p{L}\s0-9-_!%&()=\[\]#@,.;+]+',
-            'address'       => '[\p{L}0-9\s.,()°-]+',
-            'date_dmy'      => '[0-9]{1,2}\-[0-9]{1,2}\-[0-9]{4}',
-            'date_ymd'      => '[0-9]{4}\-[0-9]{1,2}\-[0-9]{1,2}',
-            'email'         => '[a-zA-Z0-9_.-]+@[a-zA-Z0-9-]+.[a-zA-Z0-9-.]+[.]+[a-z-A-Z]'
-        );
-        
-        /**
-         * @var array $errors
-         */
-        public $errors = array();
-        
-        /**
-         * Nome del campo
-         * 
-         * @param string $name
-         * @return this
-         */
-        public function name($name){
-            
-            $this->name = $name;
-            return $this;
-        
-        }
-        
-        /**
-         * Valore del campo
-         * 
-         * @param mixed $value
-         * @return this
-         */
-        public function value($value){
-            
-            $this->value = $value;
-            return $this;
-        
-        }
-        
-        /**
-         * File
-         * 
-         * @param mixed $value
-         * @return this
-         */
-        public function file($value){
-            
-            $this->file = $value;
-            return $this;
-        
-        }
-        
-        /**
-         * Pattern da applicare al riconoscimento
-         * dell'espressione regolare
-         * 
-         * @param string $name nome del pattern
-         * @return this
-         */
-        public function pattern($name){
-            
-            if($name == 'array'){
-                
-                if(!is_array($this->value)){
-                    $this->errors[] = 'Formato campo '.$this->name.' non valido.';
-                }
-            
-            }else{
-            
-                $regex = '/^('.$this->patterns[$name].')$/u';
-                if($this->value != '' && !preg_match($regex, $this->value)){
-                    $this->errors[] = 'Formato campo '.$this->name.' non valido.';
-                }
-                
+    public function value($value) : Validation
+    {
+        $this->value = $value;
+        return $this;
+    }
+
+    /**
+     * File
+     *
+     * @param mixed $value
+     * @return self
+     */
+    public function file($value) : Validation
+    {
+        $this->file = $value;
+        return $this;
+    }
+
+    /**
+     * Pattern to be used for regular expression matching
+     *
+     * @param string $name pattern name
+     * @return self
+     */
+    public function pattern(string $name) : Validation
+    {
+
+        if($name == 'array'){
+
+            if(!is_array($this->value)){
+                $this->errors[$this->name] = array('error' => "val_pattern");
             }
-            return $this;
-            
+
+        }elseif($name == 'email'){
+          if($this->value != '' && !filter_var($this->value, FILTER_VALIDATE_EMAIL)){
+
+              $this->errors[$this->name] = array('error' => "val_pattern");
+          }
         }
-        
-        /**
-         * Pattern personalizzata
-         * 
-         * @param string $pattern
-         * @return this
-         */
-        public function customPattern($pattern){
-            
-            $regex = '/^('.$pattern.')$/u';
+        else{
+
+            $regex = '/^('.$this->patterns[$name].')$/u';
             if($this->value != '' && !preg_match($regex, $this->value)){
-                $this->errors[] = 'Formato campo '.$this->name.' non valido.';
+                $this->errors[$this->name] = array('error' => "val_pattern");
             }
-            return $this;
-            
+
         }
-        
-        /**
-         * Campo obbligatorio
-         * 
-         * @return this
-         */
-        public function required(){
-            
-            if((isset($this->file) && $this->file['error'] == 4) || ($this->value == '' || $this->value == null)){
-                $this->errors[] = 'Campo '.$this->name.' obbligatorio.';
-            }            
-            return $this;
-            
+        return $this;
+    }
+
+    /**
+     * Custom pattern
+     *
+     * @param string $pattern
+     * @return self
+     */
+    public function customPattern(string $pattern) : Validation
+    {
+        $regex = '/^('.$pattern.')$/u';
+        if($this->value != '' && !preg_match($regex, $this->value)){
+            $this->errors[$this->name] = array('error' => "val_pattern");
         }
-        
-        /**
-         * Lunghezza minima
-         * del valore del campo
-         * 
-         * @param int $min
-         * @return this
-         */
-        public function min($length){
-            
-            if(is_string($this->value)){
-                
-                if(strlen($this->value) < $length){
-                    $this->errors[] = 'Valore campo '.$this->name.' inferiore al valore minimo';
-                }
-           
-            }else{
-                
-                if($this->value < $length){
-                    $this->errors[] = 'Valore campo '.$this->name.' inferiore al valore minimo';
-                }
-                
-            }
-            return $this;
-            
+        return $this;
+    }
+
+    /**
+     * Required field
+     *
+     * @return self
+     */
+    public function required() : Validation
+    {
+        if((isset($this->file) && $this->file['error'] == 4) || ($this->value == '' || $this->value == null)){
+            $this->errors[$this->name] = array('error' => "val_required");
         }
-            
-        /**
-         * Lunghezza massima
-         * del valore del campo
-         * 
-         * @param int $max
-         * @return this
-         */
-        public function max($length){
-            
-            if(is_string($this->value)){
-                
-                if(strlen($this->value) > $length){
-                    $this->errors[] = 'Valore campo '.$this->name.' superiore al valore massimo';
-                }
-           
-            }else{
-                
-                if($this->value > $length){
-                    $this->errors[] = 'Valore campo '.$this->name.' superiore al valore massimo';
-                }
-                
+        return $this;
+    }
+
+    /**
+     * Minimum length of field value
+     *
+     * @param int $min
+     * @return self
+     */
+    public function min(int $length) : Validation
+    {
+        if(is_string($this->value)){
+
+            if(strlen($this->value) < $length){
+                $this->errors[$this->name] = array('error' => "val_min");
             }
-            return $this;
-            
-        }
-        
-        /**
-         * Confronta con il valore di
-         * un altro campo
-         * 
-         * @param mixed $value
-         * @return this
-         */
-        public function equal($value){
-        
-            if($this->value != $value){
-                $this->errors[] = 'Valore campo '.$this->name.' non corrispondente.';
+
+        }else{
+
+            if($this->value < $length){
+                $this->errors[$this->name] = array('error' => "val_min");
             }
-            return $this;
-            
+
         }
-        
-        /**
-         * Dimensione massima del file 
-         *
-         * @param int $size
-         * @return this 
-         */
-        public function maxSize($size){
-            
-            if($this->file['error'] != 4 && $this->file['size'] > $size){
-                $this->errors[] = 'Il file '.$this->name.' supera la dimensione massima di '.number_format($size / 1048576, 2).' MB.';
+        return $this;
+    }
+
+    /**
+     * Maximum length of field value
+     *
+     * @param int $max
+     * @return self
+     */
+    public function max($length) : Validation
+    {
+        if(is_string($this->value)){
+
+            if(strlen($this->value) > $length){
+                $this->errors[$this->name] = array('error' => "val_max");
             }
-            return $this;
-            
-        }
-        
-        /**
-         * Estensione (formato) del file
-         *
-         * @param string $extension
-         * @return this 
-         */
-        public function ext($extension){
-
-            if($this->file['error'] != 4 && pathinfo($this->file['name'], PATHINFO_EXTENSION) != $extension && strtoupper(pathinfo($this->file['name'], PATHINFO_EXTENSION)) != $extension){
-                $this->errors[] = 'Il file '.$this->name.' non è un '.$extension.'.';
+
+        }else{
+
+            if($this->value > $length){
+                $this->errors[$this->name] = array('error' => "val_max");
             }
-            return $this;
-            
+
         }
-        
-        /**
-         * Purifica per prevenire attacchi XSS
-         *
-         * @param string $string
-         * @return $string
-         */
-        public function purify($string){
-            return htmlspecialchars($string, ENT_QUOTES, 'UTF-8');
+        return $this;
+    }
+
+    /**
+     * Compare with the value of another field
+     *
+     * @param mixed $value
+     * @return self
+     */
+    public function equal($value) : Validation
+    {
+        if($this->value != $value){
+            $this->errors[$this->name] = array('error' => "val_equal");
         }
-        
-        /**
-         * Campi validati
-         * 
-         * @return boolean
-         */
-        public function isSuccess(){
-            if(empty($this->errors)) return true;
+        return $this;
+    }
+
+    /**
+     * Maximum file size
+     *
+     * @param int $size
+     * @return self
+     */
+    public function maxSize(int $size) : Validation
+    {
+        if($this->file['error'] != 4 && $this->file['size'] > $size){
+            $this->errors[$this->name] = array('error' => "val_file_max_size", 'size' => number_format($size / 1048576, 2));
         }
-        
-        /**
-         * Errori della validazione
-         * 
-         * @return array $this->errors
-         */
-        public function getErrors(){
-            if(!$this->isSuccess()) return $this->errors;
+        return $this;
+    }
+
+    /**
+     * File extension
+     *
+     * @param string $extension
+     * @return self
+     */
+    public function ext(string $extension) : Validation
+    {
+        if($this->file['error'] != 4 && pathinfo($this->file['name'], PATHINFO_EXTENSION) != $extension && strtoupper(pathinfo($this->file['name'], PATHINFO_EXTENSION)) != $extension){
+            $this->errors[$this->name] = array('error' => "val_file_ext", 'ext' => $extension);
         }
-        
-        /**
-         * Visualizza errori in formato Html
-         * 
-         * @return string $html
-         */
-        public function displayErrors(){
-            
-            $html = '<ul>';
-                foreach($this->getErrors() as $error){
-                    $html .= '<li>'.$error.'</li>';
-                }
-            $html .= '</ul>';
-            
-            return $html;
-            
+        return $this;
+    }
+
+    /**
+     * Sanitize against XSS attacks
+     *
+     * @param string $string
+     * @return $string
+     */
+    public function purify(string $string) : string
+    {
+        return htmlspecialchars($string, ENT_QUOTES, 'UTF-8');
+    }
+
+    /**
+     * Check if fields are valid
+     *
+     * @return boolean
+     */
+    public function isSuccess() : bool
+    {
+        return empty($this->errors);
+    }
+
+    /**
+     * Validation errors
+     *
+     * @return array $this->errors
+     */
+    public function getErrors() : array|null
+    {
+        if(!$this->isSuccess()){
+            return $this->errors;
+        }else{
+            return null;
         }
-        
-        /**
-         * Visualizza risultato della validazione
-         *
-         * @return booelan|string
-         */
-        public function result(){
-            
-            if(!$this->isSuccess()){
-               
-                foreach($this->getErrors() as $error){
-                    echo "$error\n";
-                }
-                exit;
-                
-            }else{
-                return true;
+    }
+
+    /**
+     * Display errors in HTML format
+     *
+     * @return string $html
+     */
+    public function displayErrors() : string
+    {
+        $html = '<ul>';
+            foreach($this->getErrors() as $name => $error){
+                $html .= '<li>'.$name." - ".LANG['val_errors'][$error['error']].'</li>';
+            }
+        $html .= '</ul>';
+
+        return $html;
+    }
+
+    /**
+     * Display validation result
+     *
+     * @return void
+     */
+    public function result() : void
+    {
+        if(!$this->isSuccess()){
+            foreach($this->getErrors() as $error){
+                echo "$error\n";
             }
-        
         }
-        
-        /**
-         * Verifica se il valore è
-         * un numero intero
-         *
-         * @param mixed $value
-         * @return boolean
-         */
-        public static function is_int($value){
-            if(filter_var($value, FILTER_VALIDATE_INT)) return true;
+    }
+
+    /**
+     * Check if value is an integer
+     *
+     * @param mixed $value
+     * @return boolean
+     */
+    public static function is_int($value) : bool
+    {
+        if(filter_var($value, FILTER_VALIDATE_INT)){
+            return true;
+        }else{
+            return false;
         }
-        
-        /**
-         * Verifica se il valore è
-         * un numero float
-         *
-         * @param mixed $value
-         * @return boolean
-         */
-        public static function is_float($value){
-            if(filter_var($value, FILTER_VALIDATE_FLOAT)) return true;
+    }
+
+    /**
+     * Check if value is a float
+     *
+     * @param mixed $value
+     * @return boolean
+     */
+    public static function is_float($value) : bool
+    {
+        if(filter_var($value, FILTER_VALIDATE_FLOAT)){
+            return true;
+        }else{
+            return false;
         }
-        
-        /**
-         * Verifica se il valore è
-         * una lettera dell'alfabeto
-         *
-         * @param mixed $value
-         * @return boolean
-         */
-        public static function is_alpha($value){
-            if(filter_var($value, FILTER_VALIDATE_REGEXP, array('options' => array('regexp' => "/^[a-zA-Z]+$/")))) return true;
+    }
+
+    /**
+     * Check if value is an alphabetic character
+     *
+     * @param mixed $value
+     * @return boolean
+     */
+    public static function is_alpha($value) : bool
+    {
+        if(filter_var($value, FILTER_VALIDATE_REGEXP, array('options' => array('regexp' => "/^[a-zA-Z]+$/")))){
+            return true;
+        }else{
+            return false;
         }
-        
-        /**
-         * Verifica se il valore è
-         * una lettera o un numero
-         *
-         * @param mixed $value
-         * @return boolean
-         */
-        public static function is_alphanum($value){
-            if(filter_var($value, FILTER_VALIDATE_REGEXP, array('options' => array('regexp' => "/^[a-zA-Z0-9]+$/")))) return true;
+    }
+
+    /**
+     * Check if value is an alphanumeric character
+     *
+     * @param mixed $value
+     * @return boolean
+     */
+    public static function is_alphanum($value) : bool
+    {
+        if(filter_var($value, FILTER_VALIDATE_REGEXP, array('options' => array('regexp' => "/^[a-zA-Z0-9]+$/")))){
+            return true;
+        }else{
+            return false;
         }
-        
-        /**
-         * Verifica se il valore è
-         * un url
-         *
-         * @param mixed $value
-         * @return boolean
-         */
-        public static function is_url($value){
-            if(filter_var($value, FILTER_VALIDATE_URL)) return true;
+    }
+
+    /**
+     * Check if value is a URL
+     *
+     * @param mixed $value
+     * @return boolean
+     */
+    public static function is_url($value) : bool
+    {
+        if(filter_var($value, FILTER_VALIDATE_URL)) {
+            return true;
+        }else{
+            return false;
         }
-        
-        /**
-         * Verifica se il valore è
-         * un uri
-         *
-         * @param mixed $value
-         * @return boolean
-         */
-        public static function is_uri($value){
-            if(filter_var($value, FILTER_VALIDATE_REGEXP, array('options' => array('regexp' => "/^[A-Za-z0-9-\/_]+$/")))) return true;
+    }
+
+    /**
+     * Check if value is a URI
+     *
+     * @param mixed $value
+     * @return boolean
+     */
+    public static function is_uri($value) : bool
+    {
+        if(filter_var($value, FILTER_VALIDATE_REGEXP, array('options' => array('regexp' => "/^[A-Za-z0-9-\/_?&=]+$/")))){
+            return true;
+        }else{
+            return false;
         }
-        
-        /**
-         * Verifica se il valore è
-         * true o false
-         *
-         * @param mixed $value
-         * @return boolean
-         */
-        public static function is_bool($value){
-            if(is_bool(filter_var($value, FILTER_VALIDATE_BOOLEAN, FILTER_NULL_ON_FAILURE))) return true;
+    }
+
+    /**
+     * Check if value is true or false
+     *
+     * @param mixed $value
+     * @return boolean
+     */
+    public static function is_bool($value) : bool
+    {
+        if(filter_var($value, FILTER_VALIDATE_BOOLEAN)) {
+            return true;
+        }else{
+            return false;
         }
-        
-        /**
-         * Verifica se il valore è
-         * un'e-mail
-         *
-         * @param mixed $value
-         * @return boolean
-         */
-        public static function is_email($value){
-            if(filter_var($value, FILTER_VALIDATE_EMAIL)) return true;
+    }
+
+    /**
+     * Check if value is an email address
+     *
+     * @param mixed $value
+     * @return boolean
+     */
+    public static function is_email($value) : bool
+    {
+        if(filter_var($value, FILTER_VALIDATE_EMAIL)) {
+            return true;
+        }else{
+            return false;
         }
-        
-    }
\ No newline at end of file
+    }
+
+}