How to Add Google Authenticator (2FA) in CodeIgniter Login

In today’s digital world, security is not optional—it’s a necessity. A simple username and password login system is no longer enough. Hackers can easily steal or guess weak passwords.

To solve this, developers use Two-Factor Authentication (2FA). In this blog, we’ll see how to implement Google Authenticator in a CodeIgniter (CI) application in a simple and user-friendly way.

📌 What is Google Authenticator?

Google Authenticator is a free mobile app available on Android and iOS. It generates a 6-digit OTP (One Time Password) that changes every 30 seconds.

When you integrate it into your CodeIgniter project:

• The user enters their username.
• Instead of a password, they enter the OTP from Google Authenticator.
• If the OTP matches, login is successful.

👉 This makes login faster, safer, and easier for users.

🛠 Step 1: Install Google Authenticator Library

1. Go to this repository: ci-google-authenticator

2. Download the file:

application/libraries/GoogleAuthenticator.php 

3. Place it in your CodeIgniter project under:

/application/libraries/GoogleAuthenticator.php 

4. Load it in your controller:

$this->load->library('GoogleAuthenticator'); 

🛠 Step 2: Generate a Secret Key & QR Code

When a user registers for the first time, generate a secret key and QR code for their account. They will scan it in the Google Authenticator app.

Controller Example:

class Login extends CI_Controller { 

    public function setup_authenticator() { 

        $ga = new PHPGangsta_GoogleAuthenticator(); 

        // Generate secret key 

        $secret = $ga->createSecret(); 

        // Generate QR Code 

        $qrCodeUrl = $ga->getQRCodeGoogleUrl('MyCompanyApp', $secret); 

        // Save secret key in database for the user 

        $this->db->set('ga_secret', $secret) 

                 ->where('id', $this->session->userdata('user_id')) 

                 ->update('users'); 

        // Pass QR code to view 

        $data['qrCodeUrl'] = $qrCodeUrl; 

        $this->load->view('authenticator_setup', $data); 

    } 

} 

👉 The user scans this QR code in their Google Authenticator app and starts generating OTPs.

🛠 Step 3: Verify OTP During Login

Controller Example:

public function verify_login() { 

    $ga = new PHPGangsta_GoogleAuthenticator(); 

    $username = $this->input->post('username'); 

    $otp = $this->input->post('otp'); 

    // Fetch user by username 

    $user = $this->db->get_where('users', ['username' => $username])->row(); 

    if (!$user) { 

        $this->session->set_flashdata('error', 'Invalid Username'); 

        redirect('login'); 

    } 

    $secret = $user->ga_secret; 

    // Verify OTP 

    $checkResult = $ga->verifyCode($secret, $otp, 2); 

    if ($checkResult) { 

        // OTP correct → Login success 

        $this->session->set_userdata('user_id', $user->id); 

        redirect('dashboard'); 

    } else { 

        // OTP incorrect 

        $this->session->set_flashdata('error', 'Invalid OTP. Try again.'); 

        redirect('login'); 

    } 

} 

🛠 Step 4: Create a Simple Login Form

<form action="<?= base_url('login/verify_login') ?>" method="post">
    <label for="username">Username</label>
    <input type="text" name="username" required>

    <label for="otp">Authenticator OTP</label>
    <input type="text" name="otp" required>

    <button type="submit">Login</button>
</form>

✅ Why Use Google Authenticator in CodeIgniter?

• Stronger Security – Protects user accounts even if passwords are leaked.
• No Extra Cost – Free mobile app, no SMS charges.
• User Friendly – Just enter username + OTP, no password required.
• SEO Benefit – Adding 2FA increases trust for your web application and brand.

🎯 Conclusion

By integrating Google Authenticator 2FA directly with username + OTP login, you can make your CodeIgniter application:

• More secure,
• More user-friendly,
• And more professional.