public function registration_post(){

  $jsonArray = json_decode(file_get_contents('php://input'),true);
  $user_name = $jsonArray['user_name'];
  $email = $jsonArray['email'];
  $password = $jsonArray['password'];

    $result = $this->reg_model->insert_api($user_name,$email,$password);
        if ($result){
            $this->load->library('email');
            $from_email = "abc@gmail.com";
            $this->email->from($from_email, 'Name');
            $this->email->to($email);
            $this->email->subject('email subject');
            $message = 'email body';
            $this->email->message($message);
            $this->email->send();
            $data = $this->response($this->reg_model->get($user_name));
        }
}