The GAuth library is designed to generate and validate codes compatible with the Google Authenticator tools.

Include in your composer.json file:

{
    "require": {
        "enygma/gauth": "dev-master"
    }
}

To get started using the Google Authenticator with your application, you'll need to make an initialization key (using generateCode) and save that to your app's settings. This is the code you'll share with your users when they're trying to set up their client for your system.

Then, when they log in you have them enter in the latest code listed for your application for thier account.

NOTE: This tool offers a "window of opportunity" for the codes of 2 seconds forward and backward of the current timestamp, just in case things are a bit off. You can change this with the setRange method:

<?php
$g = new \GAuth\Auth();
// set it to 3 seconds
$g->setRange(3);
?>

<?php
require_once 'vendor/autoload.php';
// Useful for creating a new Initialization key if needed
$g = new \GAuth\Auth();
$code = $g->generateCode();
var_dump($code);
?>

<?php
$code = 'code-inputted-from-user';
$g = new \GAuth\Auth('your-initialization-code');
$verify = $g->validateCode($code);
if ($verify == true) {
    echo 'User code verified!';
} else {
    echo 'User code invalid!';
}
?>

You can also use the tool to get the URL for a QR code users can scan to add your application to their Authenticator client. The call to generateQrImage returns the actual image data for you to use as you wish, either to embed in an img tag or save to a file:

<?php
$holder = 'foo@bar.com';
$name = 'my-app-name';
$g = new \GAuth\Auth('your-initialization-code');
$qrCodeImageData = $g->generateQrImage($holder, $name, 200);
// To use in an image tag:
echo '<img src="data:image/png;base64,'.base64_encode($qrCodeImageData).'"/><br/><hr/>';
// Or just save to a file
file_put_contents('/path/to/qr-file.png', $qrCodeImageData);
?>

The library uses internal QR code generation, not the Google Charts API many similar libraries use.

• Google TOTP Two-factor Authentication for PHP
• Links to client for smartphones