google captcha not working

my view file
*********
 <div class="g-recaptcha" data-sitekey="">

Controller file
***********
public function loginMe()
    {
       
        $this->load->library('form_validation');

            $this->load->library('session'); 
            $this->load->helper('url'); 
        
        $this->form_validation->set_rules('regno', 'regno','required');
        $this->form_validation->set_rules('dob', 'dob','required');

        
        if($this->form_validation->run() == FALSE)
        {
            $this->index();
            //echo "test";

        }
        else
        {
            $regno = $this->security->xss_clean($this->input->post('regno'));
            //echo $regno;
            $dob = $this->input->post('dob');
            //echo $dob;
            
            $result = $this->login_model->loginMe($regno, $dob);
            //print_r($result);

            
            if(!empty($result))
            {
                $lastLogin = $this->login_model->lastLoginInfo($result->regno);
                print_r($lastLogin);


                $sessionArray = array('userId'=>$result->regno,                    
                                        'role'=>$result->roleId,
                                        'roleText'=>$result->role,
                                        'name'=>$result->name,

                                        'lastLogin'=> $lastLogin->createdDtm,

                                        'isLoggedIn' => TRUE
                                );
                print_r($sessionArray);

                $this->session->set_userdata($sessionArray);

                unset($sessionArray['userId'], $sessionArray['isLoggedIn'], $sessionArray['lastLogin']);

                $loginInfo = array("userId"=>$result->regno, "sessionData" => json_encode($sessionArray), "machineIp"=>$_SERVER['REMOTE_ADDR'], "userAgent"=>1, "agentString"=>1, "platform"=>'A');

                $this->login_model->lastLogin($loginInfo);
                
                redirect('/dashboard');
            }
            else
            {
                $this->session->set_flashdata('error', 'Email or password mismatch');
                
                redirect('/login');
            }
        }
    }

public function recaptcha($str='')
  {
    $google_url="https://www.google.com/recaptcha/api/siteverify";
    $secret=' ';
    $ip=$_SERVER['REMOTE_ADDR'];
    $url=$google_url."?secret=".$secret."&response=".$str."&remoteip=".$ip;
    $curl = curl_init();
    curl_setopt($curl, CURLOPT_URL, $url);
    curl_setopt($curl, CURLOPT_RETURNTRANSFER, 1);
    curl_setopt($curl, CURLOPT_TIMEOUT, 10);
    curl_setopt($curl, CURLOPT_USERAGENT, "Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2.16) Gecko/20110319 Firefox/3.6.16");
    $res = curl_exec($curl);
    curl_close($curl);
    $res= json_decode($res, true);
    //reCaptcha success check
    if($res['success'])
    {
      return TRUE;
    }
    else
    {
      $this->form_validation->set_message('recaptcha', 'The reCAPTCHA field is telling me that you are a robot. Shall we give it another try?');
      return FALSE;
    }
  }


I want to add google captcha with validation of only (Regno field and Google captcha)
I tried with these possibilities. whats wrong in my code?

I want to add google captcha with validation of only (Regno field and Google captcha)

remove

PHP Code:

$this->form_validation->set_rules('dob', 'dob','required'); 


and add the recaptcha function as a validation callback.
https://codeigniter.com/user_guide/libra...on-methods

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