I want create register page and for this i write php codes. but when show result in json, not show UTF-8 characters!
my code:
<?php
require_once 'DBOperations.php';
class Functions{
private $db;
public function __construct() {
      $this -> db = new DBOperations();
}
public function registerUser($name, $email, $password) {
   $db = $this -> db;
   if (!empty($name) && !empty($email) && !empty($password)) {
      if ($db -> checkUserExist($email)) {
         $response["result"] = "failure";
         $response["message"] = "اين ايميل قبلا ثبت شده است";
         return json_encode($response);
      } else {
         $result = $db -> insertData($name, $email, $password);
         if ($result) {
              $response["result"] = "success";
            $response["message"] = "تبريک، در کلوني عضو شدي";
            return json_encode($response);
         } else {
            $response["result"] = "failure";
            $response["message"] = "ثبت نام با خطا روبرو شده است";
            return json_encode($response);
         }
      }
   } else {
      return $this -> getMsgParamNotEmpty();
   }
}
public function loginUser($email, $password) {
  $db = $this -> db;
  if (!empty($email) && !empty($password)) {
    if ($db -> checkUserExist($email)) {
       $result =  $db -> checkLogin($email, $password);
       if(!$result) {
        $response["result"] = "failure";
        $response["message"] = "ايميل يا کلمه عبور اشتباه است";
        return json_encode($response);
       } else {
        $response["result"] = "success";
        $response["message"] = "با موفقيت وارد شديد";
        $response["user"] = $result;
        return json_encode($response);
       }
    } else {
      $response["result"] = "failure";
      $response["message"] = "خطا در اطلاعات وارد شده";
      return json_encode($response);
    }
  } else {
      return $this -> getMsgParamNotEmpty();
    }
}
public function changePassword($email, $old_password, $new_password) {
  $db = $this -> db;
  if (!empty($email) && !empty($old_password) && !empty($new_password)) {
    if(!$db -> checkLogin($email, $old_password)){
      $response["result"] = "failure";
      $response["message"] = "کلمه عبور قبلي نادرست است";
      return json_encode($response);
    } else {
    $result = $db -> changePassword($email, $new_password);
      if($result) {
        $response["result"] = "success";
        $response["message"] = "کلمه عبور با موفقيت تغيير يافت";
        return json_encode($response);
      } else {
        $response["result"] = "failure";
        $response["message"] = 'خطا در تغيير کلمه عبور';
        return json_encode($response);
      }
    }
  } else {
      return $this -> getMsgParamNotEmpty();
  }
}
public function isEmailValid($email){
  return filter_var($email, FILTER_VALIDATE_EMAIL);
}
public function getMsgParamNotEmpty(){
  $response["result"] = "failure";
  $response["message"] = "فيلدها نبايد خالي باشند";
  return json_encode($response);
}
public function getMsgInvalidParam(){
  $response["result"] = "failure";
  $response["message"] = "فيلدها نامعتبر هستند";
  return json_encode($response);
}
public function getMsgInvalidEmail(){
  $response["result"] = "failure";
  $response["message"] = "ايميل نامعتبر است";
  return json_encode($response);
}
}
How can i show "message" for utf-8 in json?