Вот несколько методов реализации двухфакторной аутентификации (2FA) в PHP, а также примеры кода:

1. Одноразовый пароль на основе времени (TOTP) с использованием Google Authenticator:

   // Install the "robthree/twofactorauth" library using Composer
   require_once 'vendor/autoload.php';
   use RobThree\Auth\TwoFactorAuth;
   $secret = 'your_secret_key';
   $totp = new TwoFactorAuth('YourApp');
   $qrCodeUrl = $totp->getQRCodeImageAsDataUri('YourApp:username', $secret);
   // Verify the code
   $code = $_POST['code'];
   $isValid = $totp->verifyCode($secret, $code);
   if ($isValid) {
   // Code is valid, proceed with authentication
   } else {
   // Code is invalid, show error message
   }

2. Подтверждение по SMS с использованием Twilio:

   // Install the "twilio/sdk" library using Composer
   require_once 'vendor/autoload.php';
   use Twilio\Rest\Client;
   $accountSid = 'your_account_sid';
   $authToken = 'your_auth_token';
   $client = new Client($accountSid, $authToken);
   $verification = $client->verify->v2->services('your_service_sid')
   ->verifications
   ->create(['to' => '+1234567890', 'channel' => 'sms']);
   // Verify the code
   $code = $_POST['code'];
   $isValid = $client->verify->v2->services('your_service_sid')
   ->verificationChecks
   ->create(['to' => '+1234567890', 'code' => $code]);
   if ($isValid->valid) {
   // Code is valid, proceed with authentication
   } else {
   // Code is invalid, show error message
   }

3. Подтверждение по электронной почте с помощью PHPMailer:

   // Install the "phpmailer/phpmailer" library using Composer
   require_once 'vendor/autoload.php';
   use PHPMailer\PHPMailer\PHPMailer;
   $mail = new PHPMailer();
   $mail->isSMTP();
   $mail->Host = 'smtp.example.com';
   $mail->SMTPAuth = true;
   $mail->Username = 'your_username';
   $mail->Password = 'your_password';
   $mail->SMTPSecure = 'tls';
   $mail->Port = 587;
   $mail->setFrom('from@example.com', 'Your Name');
   $mail->addAddress('to@example.com', 'Recipient Name');
   $mail->Subject = 'Two-Factor Authentication';
   $mail->Body = 'Your verification code is: 123456';
   // Send the email
   if ($mail->send()) {
   // Code sent successfully, proceed with authentication
   } else {
   // Error sending the code, show error message
   }