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PHP class to generate and verify Google Authenticator 2-factor authentication
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Google Authenticator PHP class

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This PHP class can be used to interact with the Google Authenticator mobile app for 2-factor-authentication. This class can generate secrets, generate codes, validate codes and present a QR-Code for scanning the secret. It implements TOTP according to RFC6238

For a secure installation you have to make sure that used codes cannot be reused (replay-attack). You also need to limit the number of verifications, to fight against brute-force attacks. For example you could limit the amount of verifications to 10 tries within 10 minutes for one IP address (or IPv6 block). It depends on your environment.


See following example:

require_once 'PHPGangsta/GoogleAuthenticator.php';

$ga = new PHPGangsta_GoogleAuthenticator();
$secret = $ga->createSecret();
echo "Secret is: ".$secret."\n\n";

$qrCodeUrl = $ga->getQRCodeGoogleUrl('Blog', $secret);
echo "Google Charts URL for the QR-Code: ".$qrCodeUrl."\n\n";

$oneCode = $ga->getCode($secret);
echo "Checking Code '$oneCode' and Secret '$secret':\n";

$checkResult = $ga->verifyCode($secret, $oneCode, 2);    // 2 = 2*30sec clock tolerance
if ($checkResult) {
    echo 'OK';
} else {
    echo 'FAILED';

Running the script provides the following output:


Google Charts URL for the QR-Code:|0&cht=qr&chl=otpauth://totp/

Checking Code '848634' and Secret 'OQB6ZZGYHCPSX4AK':


  • Use Composer to install the package

  • From project root directory execute following

composer install

  • Composer will take care of autoloading the library. Just include the following at the top of your file

    require_once __DIR__ . '/../vendor/autoload.php';

Run Tests:

  • All tests are inside tests folder.
  • Execute composer install and then run the tests from project root directory
  • Run as phpunit tests from the project root directory


  • ??? What do you need?


If you like this script or have some features to add: contact me, visit my blog, fork this project, send pull requests, you know how it works.

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