Two factor authentication with Google Authenticator and PHP

In this tutorial, I have explained how to add Two factor authentication with Google Authenticator and PHP . You can check official Google-Authentication project here. Github

Follow the steps.

Step 1) Create a unique secret code of length 16 characters.
PHPGangsta provides wrapper class for Google Authenticator. You can download using composer.

curl -sS | php
php composer.phar require  phpgangsta/googleauthenticator:dev-master

Use the below code to generate the secret code.

require 'vendor/autoload.php';
$authenticator = new PHPGangsta_GoogleAuthenticator();
$secret = $authenticator->createSecret();
echo "Secret: ".$secret;



Step 2) Create a QR code withe the generated secret.

We need to prepare a QR code using the secret. If you want to read more about QR code generation for Google Authenticator. Github Wiki
You can use any QR code generator to generate the QR code, For this demo I am using Google charts.

require 'vendor/autoload.php';
$authenticator = new PHPGangsta_GoogleAuthenticator();
$secret = $authenticator->createSecret();
echo "Secret: ".$secret."\n";  //save this at server side

$website = ''; //Your Website
$title= 'Hayageek';
$qrCodeUrl = $authenticator->getQRCodeGoogleUrl($title, $secret,$website);
echo $qrCodeUrl;



Step 3) Generate TOTP (Time-Based One time password) using Google Authenticator App

Download the Google Authenticator app from Google Play or AppStore

Open the app and Click on ‘+’ Button, and scan the QR code generated using Google Charts. Authenticator app generates the TOTP for your website. TOTP will change for every 30 secs.

Two factor authentication with Google Authenticator

Step 4) Verifying OTP at server side

require 'vendor/autoload.php';
$authenticator = new PHPGangsta_GoogleAuthenticator();

$secret = '3JMZE4ASZRIISJRI'; //This is used to generate QR code
$otp = '183036' ;//Generated by Authenticator.

$tolerance = 0;
	//Every otp is valid for 30 sec.
	// If somebody provides OTP at 29th sec, by the time it reaches the server OTP is expired.
	//So we can give tolerance =1, it will check current  & previous OTP.
	// tolerance =2, verifies current and last two OTPS

$checkResult = $authenticator->verifyCode($secret, $otp, $tolerance);    

if ($checkResult) 
    echo 'OTP is Validated Succesfully';
} else {
    echo 'FAILED';


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I am a developer and I maintain the site The best software developers are those who can think like both a developer and a user.
All posts by Ravishanker Kusuma